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GHSA-MHRX-XQMX-R77G

Vulnerability from github – Published: 2025-10-09 15:31 – Updated: 2026-02-03 15:30

Details

In the Linux kernel, the following vulnerability has been resolved:

rxrpc: Fix untrusted unsigned subtract

Fix the following Smatch static checker warning:

net/rxrpc/rxgk_app.c:65 rxgk_yfs_decode_ticket() warn: untrusted unsigned subtract. 'ticket_len - 10 * 4'

by prechecking the length of what we're trying to extract in two places in the token and decoding for a response packet.

Also use sizeof() on the struct we're extracting rather specifying the size numerically to be consistent with the other related statements.

Severity

7.8 (High)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2025-39962"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-787"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-10-09T13:15:32Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nrxrpc: Fix untrusted unsigned subtract\n\nFix the following Smatch static checker warning:\n\n   net/rxrpc/rxgk_app.c:65 rxgk_yfs_decode_ticket()\n   warn: untrusted unsigned subtract. \u0027ticket_len - 10 * 4\u0027\n\nby prechecking the length of what we\u0027re trying to extract in two places in\nthe token and decoding for a response packet.\n\nAlso use sizeof() on the struct we\u0027re extracting rather specifying the size\nnumerically to be consistent with the other related statements.",
  "id": "GHSA-mhrx-xqmx-r77g",
  "modified": "2026-02-03T15:30:20Z",
  "published": "2025-10-09T15:31:03Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-39962"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2429a197648178cd4dc930a9d87c13c547460564"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/71571e187106631a8127f2dde780f35caa358d33"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2025-39962 (GCVE-0-2025-39962)

Vulnerability from cvelistv5 – Published: 2025-10-09 12:13 – Updated: 2026-08-05 12:06

Title

rxrpc: Fix untrusted unsigned subtract

Summary

In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix untrusted unsigned subtract Fix the following Smatch static checker warning: net/rxrpc/rxgk_app.c:65 rxgk_yfs_decode_ticket() warn: untrusted unsigned subtract. 'ticket_len - 10 * 4' by prechecking the length of what we're trying to extract in two places in the token and decoding for a response packet. Also use sizeof() on the struct we're extracting rather specifying the size numerically to be consistent with the other related statements.

Severity

7.5 (High)


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

Assigner

Linux mitre root Scorecard

References

2 references

URL	Tags
https://git.kernel.org/stable/c/71571e187106631a8…
https://git.kernel.org/stable/c/2429a197648178cd4…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 9d1d2b59341f58126a69b51f9f5f8ccb9f12e54a , < 71571e187106631a8127f2dde780f35caa358d33 (git) Affected: 9d1d2b59341f58126a69b51f9f5f8ccb9f12e54a , < 2429a197648178cd4dc930a9d87c13c547460564 (git)
Linux	Linux	Affected: 6.16 Unaffected: 0 , < 6.16 (semver) Unaffected: 6.16.9 , ≤ 6.16.* (semver) Unaffected: 6.17 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/rxrpc/rxgk_app.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "71571e187106631a8127f2dde780f35caa358d33",
              "status": "affected",
              "version": "9d1d2b59341f58126a69b51f9f5f8ccb9f12e54a",
              "versionType": "git"
            },
            {
              "lessThan": "2429a197648178cd4dc930a9d87c13c547460564",
              "status": "affected",
              "version": "9d1d2b59341f58126a69b51f9f5f8ccb9f12e54a",
              "versionType": "git"
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          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.16"
            },
            {
              "lessThan": "6.16",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.16.*",
              "status": "unaffected",
              "version": "6.16.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.17",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "6.16",
                  "vulnerable": true
                },
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      "descriptions": [
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nrxrpc: Fix untrusted unsigned subtract\n\nFix the following Smatch static checker warning:\n\n   net/rxrpc/rxgk_app.c:65 rxgk_yfs_decode_ticket()\n   warn: untrusted unsigned subtract. \u0027ticket_len - 10 * 4\u0027\n\nby prechecking the length of what we\u0027re trying to extract in two places in\nthe token and decoding for a response packet.\n\nAlso use sizeof() on the struct we\u0027re extracting rather specifying the size\nnumerically to be consistent with the other related statements."
        }
      ],
      "metrics": [
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            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The vulnerable code parses RxGK RESPONSE packets received over UDP by an rxrpc server connection; the AFS cache manager (present on every kafs client) exposes this path to remote peers on the network.\nAC:L - A single crafted RESPONSE packet with a small token_len and oversized ticket_len reliably bypasses the check and triggers the crash; the required server key exists by default on the CM and kvno/enctype are standard, with no attacker-uncontrolled conditions.\nPR:N - The malformed length is processed during the challenge/response handshake (CONN_SERVICE_CHALLENGING), before any credential is verified, so no authentication or privileges are required.\nUI:N - Exploitation is fully driven by attacker-sent network packets; no action by any local user is needed.\nS:U - The impact is confined to the kernel that processes the packet; no crossing of a security/authority boundary such as VM or IOMMU escape occurs.\nC:N - The reliably reachable path is a BUG_ON crash with no data returned to the attacker; the OOB-read variant requires server-key knowledge to control decrypted content and its data is stored in a no-leak key, so there is no defensible information disclosure.\nI:N - The reachable outcome is a kernel panic in skb_to_sgvec; the length-check bypass does not yield an attacker-controlled write primitive (the payload allocation scales with the corrupted length), so no data modification results.\nA:H - The oversized attacker-controlled length reaches skb_to_sgvec and triggers BUG_ON(len), causing a kernel panic \u2014 a remote, unauthenticated denial of service."
            }
          ]
        }
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        "dateUpdated": "2026-08-05T12:06:31.023Z",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-39962",
    "datePublished": "2025-10-09T12:13:22.684Z",
    "dateReserved": "2025-04-16T07:20:57.149Z",
    "dateUpdated": "2026-08-05T12:06:31.023Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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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.

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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GHSA-MHRX-XQMX-R77G

CVE-2025-39962 (GCVE-0-2025-39962)

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