{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "go.opentelemetry.io/obi"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.9.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-45681"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-125",
      "CWE-130"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-18T20:11:20Z",
    "nvd_published_at": "2026-06-02T16:16:42Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nThe per-CPU message-buffer fallback path uses a 256-byte backup buffer but preserves the original payload size, which can be up to 8KB. If a CPU mismatch occurs, OBI can read beyond the fallback buffer and leak adjacent memory into telemetry.\n\n### Details\n\nhttps://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/032473449b53d9f02ec4619d4f5b84e6a81db362/bpf/common/http_buf_size.h#L4-L7\n\n`k_kprobes_http2_buf_size` is defined as 256 bytes, the size of the fallback buffer.\n\nhttps://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/032473449b53d9f02ec4619d4f5b84e6a81db362/bpf/common/msg_buffer.h#L12-L36\n\nIntroduces 8KB per-CPU buffer and 256-byte `fallback_buf` in `msg_buffer_t`, creating a size mismatch for fallback use.\n\nhttps://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/032473449b53d9f02ec4619d4f5b84e6a81db362/bpf/generictracer/k_tracer.c#L370-L394\n\nOn CPU mismatch, `fallback_buf `is used but size is still set to `m_buf-\u003ereal_size` (up to 8KB) and passed downstream.\n\nhttps://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/032473449b53d9f02ec4619d4f5b84e6a81db362/bpf/generictracer/protocol_http.h#L412-L441\n\n`bytes_len (from m_buf-\u003ereal_size)` is used to read payload data from `u_buf`; if `u_buf` is the 256B fallback, this can over-read and leak memory into telemetry.\n\nhttps://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/032473449b53d9f02ec4619d4f5b84e6a81db362/bpf/tpinjector/tpinjector.c#L192-L206\n\n`real_size `is set up to 8192 bytes and stored with `cpu_id`; `fallback_buf `only contains 256 bytes.\n\n### PoC\n\nLocal testing with an AddressSanitizer user-space PoC reproduced the same class of size-mismatch over-read as the vulnerable fallback-buffer path. That result is sufficient to ground the advisory in a fresh local reproduction even though the exact end-to-end eBPF path still depends on host BPF capabilities.\n\nTo reproduce the validated behavior locally:\n\n1. create a struct that models `fallback_buf[256]` and `real_size`\n2. populate only the 256-byte fallback buffer\n3. simulate the CPU mismatch path by using the fallback buffer as the source pointer while preserving a much larger `real_size`\n4. perform a read of `real_size` bytes from that 256-byte backing store under ASan\n\nAn equivalent reproducer is:\n\n```c\n// save as /tmp/poc_msgbuf_oob.c\n#include \u003cstdint.h\u003e\n#include \u003cstdio.h\u003e\n#include \u003cstring.h\u003e\n\nstruct msg_buffer {\n  unsigned char fallback_buf[256];\n  uint16_t pos;\n  uint16_t real_size;\n  uint32_t cpu_id;\n};\n\nint main(void) {\n  struct msg_buffer m = {0};\n  unsigned char sink[8192];\n\n  memset(m.fallback_buf, \u0027A\u0027, sizeof(m.fallback_buf));\n  m.real_size = 4096;\n\n  memcpy(sink, m.fallback_buf, m.real_size);\n  printf(\"copied %u bytes from a 256-byte fallback buffer\\n\", m.real_size);\n  return 0;\n}\n```\n\nCompile and run with ASan:\n\n```bash\ncc -fsanitize=address -O1 -g -o /tmp/poc_msgbuf_oob /tmp/poc_msgbuf_oob.c\nASAN_OPTIONS=abort_on_error=1 /tmp/poc_msgbuf_oob\n```\n\nExpected result:\n\n```text\nAddressSanitizer: heap-buffer-overflow or stack-buffer-overflow\n```\n\nThat user-space PoC matches the size-mismatch condition in the vulnerable code path, even though the exact end-to-end eBPF runtime path still requires host BPF attach/load capability.\n\n### Impact\n\nThis is a confidentiality issue in the HTTP tracing path. The vulnerable read occurs in OBI\u0027s local fallback-buffer handling when context propagation is enabled, the `tpinjector` sock_msg path is active, HTTP large-buffer capture is configured with a non-zero size, and a CPU mismatch occurs between producer and consumer contexts. Under those conditions, OBI can over-read from the fallback buffer and export unrelated memory through telemetry.",
  "id": "GHSA-r6c9-g6q5-qrf9",
  "modified": "2026-06-09T10:58:36Z",
  "published": "2026-05-18T20:11:20Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/security/advisories/GHSA-r6c9-g6q5-qrf9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-45681"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/releases/tag/v0.9.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "OpenTelemetry eBPF Instrumentation: CPU-mismatch fallback uses 256-byte buffer with 8KB size"
}