CVE-2025-40291 (GCVE-0-2025-40291)

Vulnerability from cvelistv5 – Published: 2025-12-08 00:46 – Updated: 2026-08-05 12:09
VLAI
Title
io_uring: fix regbuf vector size truncation
Summary
In the Linux kernel, the following vulnerability has been resolved: io_uring: fix regbuf vector size truncation There is a report of io_estimate_bvec_size() truncating the calculated number of segments that leads to corruption issues. Check it doesn't overflow "int"s used later. Rough but simple, can be improved on top.
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
Linux Linux Affected: 9ef4cbbcb4ac3786a1a4164507511b76b2a572c5 , < 826ce37a842633efe1bb763e4b13045d74060d72 (git)
Affected: 9ef4cbbcb4ac3786a1a4164507511b76b2a572c5 , < 146eb58629f45f8297e83d69e64d4eea4b28d972 (git)
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Linux Linux Affected: 6.15
Unaffected: 0 , < 6.15 (semver)
Unaffected: 6.17.8 , ≤ 6.17.* (semver)
Unaffected: 6.18 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
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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 code is reached only through io_uring SQE submission (READV_FIXED/WRITEV_FIXED, zerocopy sendmsg, fixed uring_cmd), a local syscall interface; there is no remote network trigger despite one caller being in net.c.\nAC:L - The attacker fully controls the registered buffer and the iovec lengths that drive the truncated size estimate, so the under-allocation and out-of-bounds write are triggered deterministically with no race or uncontrolled condition.\nPR:L - Any unprivileged local user can create an io_uring instance and register buffers; io_uring is enabled by default (sysctl_io_uring_disabled=0) and requires no capabilities.\nUI:N - The attacker triggers the flaw entirely through their own io_uring operations with no victim interaction required.\nS:U - The corruption occurs within kernel heap memory in the same security authority; there is no crossing of a VM/IOMMU/sandbox boundary.\nC:H - The integer-truncation-driven heap out-of-bounds access corrupts adjacent kernel objects and can be leveraged for arbitrary kernel-memory disclosure.\nI:H - The under-sized bvec allocation causes an out-of-bounds write of attacker-influenced bio_vec structures past the buffer, giving a heap write primitive exploitable for control-flow hijacking.\nA:H - The out-of-bounds heap write reliably corrupts kernel memory, causing oops/panic and denial of service."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:09:17.336Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/826ce37a842633efe1bb763e4b13045d74060d72"
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          "url": "https://git.kernel.org/stable/c/146eb58629f45f8297e83d69e64d4eea4b28d972"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40291",
    "datePublished": "2025-12-08T00:46:14.601Z",
    "dateReserved": "2025-04-16T07:20:57.185Z",
    "dateUpdated": "2026-08-05T12:09:17.336Z",
    "state": "PUBLISHED"
  },
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-30T08:38:34+00:00",
      "cve": "CVE-2025-40291",
      "id": "CVE-2025-40291",
      "initial_release_date": "2025-12-08T00:00:00+00:00",
      "product_status:known_affected": "76",
      "product_status:known_not_affected": "198",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: io_uring: fix regbuf vector size truncation",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-40291.json",
      "version": "3"
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      "current_release_date": "2026-07-25T00:31:54Z",
      "cve": "CVE-2025-40291",
      "id": "CVE-2025-40291",
      "initial_release_date": "2025-12-09T00:24:51Z",
      "product_status:known_not_affected": "408",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2025-40291",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2025-40291.json",
      "version": "8"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • 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.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • 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.


Detection rules are retrieved from Rulezet.