CVE-2025-40241 (GCVE-0-2025-40241)

Vulnerability from cvelistv5 – Published: 2025-12-04 15:31 – Updated: 2026-08-05 12:08
VLAI
Title
erofs: fix crafted invalid cases for encoded extents
Summary
In the Linux kernel, the following vulnerability has been resolved: erofs: fix crafted invalid cases for encoded extents Robert recently reported two corrupted images that can cause system crashes, which are related to the new encoded extents introduced in Linux 6.15: - The first one [1] has plen != 0 (e.g. plen == 0x2000000) but (plen & Z_EROFS_EXTENT_PLEN_MASK) == 0. It is used to represent special extents such as sparse extents (!EROFS_MAP_MAPPED), but previously only plen == 0 was handled; - The second one [2] has pa 0xffffffffffdcffed and plen 0xb4000, then "cur [0xfffffffffffff000] += bvec.bv_len [0x1000]" in "} while ((cur += bvec.bv_len) < end);" wraps around, causing an out-of-bound access of pcl->compressed_bvecs[] in z_erofs_submit_queue(). EROFS only supports 48-bit physical block addresses (up to 1EiB for 4k blocks), so add a sanity check to enforce this.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 1d191b4ca51d73699cb127386b95ac152af2b930 , < 00d8fe0b72f4ca0a983abced36aad2160038c421 (git)
Affected: 1d191b4ca51d73699cb127386b95ac152af2b930 , < a429b76114aaca3ef1aff4cd469dcf025431bd11 (git)
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Linux Linux Affected: 6.15
Unaffected: 0 , < 6.15 (semver)
Unaffected: 6.17.6 , ≤ 6.17.* (semver)
Unaffected: 6.18 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/erofs/zmap.c"
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          "vendor": "Linux",
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              "status": "affected",
              "version": "1d191b4ca51d73699cb127386b95ac152af2b930",
              "versionType": "git"
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                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "6.15",
                  "vulnerable": true
                },
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nerofs: fix crafted invalid cases for encoded extents\n\nRobert recently reported two corrupted images that can cause system\ncrashes, which are related to the new encoded extents introduced\nin Linux 6.15:\n\n  - The first one [1] has plen != 0 (e.g. plen == 0x2000000) but\n    (plen \u0026 Z_EROFS_EXTENT_PLEN_MASK) == 0. It is used to represent\n    special extents such as sparse extents (!EROFS_MAP_MAPPED), but\n    previously only plen == 0 was handled;\n\n  - The second one [2] has pa 0xffffffffffdcffed and plen 0xb4000,\n    then \"cur [0xfffffffffffff000] += bvec.bv_len [0x1000]\" in\n    \"} while ((cur += bvec.bv_len) \u003c end);\" wraps around, causing an\n    out-of-bound access of pcl-\u003ecompressed_bvecs[] in\n    z_erofs_submit_queue().  EROFS only supports 48-bit physical block\n    addresses (up to 1EiB for 4k blocks), so add a sanity check to\n    enforce this."
        }
      ],
      "metrics": [
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The vulnerable data comes from an on-disk erofs extent record, and the bug is triggered by a local `read()`/`mmap()`/readahead on a file in a mounted erofs image via `z_erofs_aops.read_folio`. There is no network-facing service that reaches `z_erofs_map_blocks_ext()`.\nAC:L - Both `m_pa` and `m_plen` are read verbatim from the crafted image, so the attacker deterministically chooses the values that make `cur + pageofs_in + pclustersize` wrap; no race, timing window, or uncontrollable memory layout is involved. Robert Morris reproduced both cases with plain image files.\nPR:L - Once the image is mounted, any unprivileged user with read access to a file triggers the path \u2014 there is no capability check on `read_folio \u2192 z_erofs_scan_folios \u2192 z_erofs_pcluster_begin \u2192 z_erofs_submit_queue`. On Android and container hosts the attacker-supplied erofs image is mounted by the platform itself, so the attacker needs only ordinary local access.\nUI:N - In the deployments where erofs carries untrusted data (Android system/APEX/OTA images, container layers over fscache/composefs, file-backed mounts), the image is mounted automatically with no human action, and the attacker then triggers the bug with their own `read()`. No victim must open a file or insert media.\nS:U - The out-of-bounds accesses to `pcl-\u003ecompressed_bvecs[]` and the oversized bio_vec target the host kernel\u0027s own heap and page allocations. No hypervisor, IOMMU, or sandbox boundary is crossed.\nC:H - `z_erofs_fill_bio_vec()` reads a `struct z_erofs_bvec` from beyond the pcluster slab object and dereferences its `.page` as a real `struct page *` (`page_folio()`, `folio-\u003eprivate`, `folio-\u003emapping`), giving an attacker-steerable kernel read; the oversized bio_vec additionally makes the kernel treat memory past a single page as an I/O buffer whose contents the decompressor copies into page-cache folios readable from userspace.\nI:H - `pcl-\u003ecompressed_bvecs[nr].page = page` in `z_erofs_fill_bio_vec()` stores a kernel pointer past the end of the pcluster slab object at an attacker-influenced index, and the expanded `bvec.bv_len = end - cur` (up to ~1 MiB on one order-0 page) lets `vfs_iocb_iter_read()` in `erofs_fileio_rq_submit()` write attacker-controlled image bytes linearly over adjacent memory \u2014 a full heap overwrite primitive.\nA:H - The maintainer reports these crafted images \"cause system crashes\"; dereferencing and refcounting a garbage `struct page *` from the out-of-bounds bvec, plus slab corruption from the out-of-bounds store, reliably produce oopses, KASAN splats, and panics."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:08:45.194Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/00d8fe0b72f4ca0a983abced36aad2160038c421"
        },
        {
          "url": "https://git.kernel.org/stable/c/a429b76114aaca3ef1aff4cd469dcf025431bd11"
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      ],
      "title": "erofs: fix crafted invalid cases for encoded extents",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40241",
    "datePublished": "2025-12-04T15:31:30.594Z",
    "dateReserved": "2025-04-16T07:20:57.181Z",
    "dateUpdated": "2026-08-05T12:08:45.194Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
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      "date": "2026-09-27",
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      "percentile": "0.0307"
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                "product": "Linux",
                "programFiles": [
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          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nerofs: fix crafted invalid cases for encoded extents\n\nRobert recently reported two corrupted images that can cause system\ncrashes, which are related to the new encoded extents introduced\nin Linux 6.15:\n\n  - The first one [1] has plen != 0 (e.g. plen == 0x2000000) but\n    (plen \u0026 Z_EROFS_EXTENT_PLEN_MASK) == 0. It is used to represent\n    special extents such as sparse extents (!EROFS_MAP_MAPPED), but\n    previously only plen == 0 was handled;\n\n  - The second one [2] has pa 0xffffffffffdcffed and plen 0xb4000,\n    then \"cur [0xfffffffffffff000] += bvec.bv_len [0x1000]\" in\n    \"} while ((cur += bvec.bv_len) \u003c end);\" wraps around, causing an\n    out-of-bound access of pcl-\u003ecompressed_bvecs[] in\n    z_erofs_submit_queue().  EROFS only supports 48-bit physical block\n    addresses (up to 1EiB for 4k blocks), so add a sanity check to\n    enforce this."
          }
        ],
        "id": "CVE-2025-40241",
        "lastModified": "2026-07-30T06:24:19.430",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
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        "published": "2025-12-04T16:16:17.250",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Deferred"
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    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2026-06-30T10:20:14+00:00",
      "cve": "CVE-2025-40241",
      "id": "CVE-2025-40241",
      "initial_release_date": "2025-12-04T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: erofs: fix crafted invalid cases for encoded extents",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-40241.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-01T13:43:05Z",
      "cve": "CVE-2025-40241",
      "id": "CVE-2025-40241",
      "initial_release_date": "2025-12-05T00:25:42Z",
      "product_status:known_not_affected": "515",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2025-40241",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2025-40241.json",
      "version": "9"
    }
  }
}



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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • 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.



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