Vulnerability-Lookup

GHSA-CX83-HXFR-M85V

Vulnerability from github – Published: 2026-06-25 09:31 – Updated: 2026-09-14 12:31

Details

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

xsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata()

The TX metadata area resides in the UMEM buffer which is memory-mapped and concurrently writable by userspace. In xsk_skb_metadata(), csum_start and csum_offset are read from shared memory for bounds validation, then read again for skb assignment. A malicious userspace application can race to overwrite these values between the two reads, bypassing the bounds check and causing out-of-bounds memory access during checksum computation in the transmit path.

Fix this by reading csum_start and csum_offset into local variables once, then using the local copies for both validation and assignment.

Note that other metadata fields (flags, launch_time) and the cached csum fields may be mutually inconsistent due to concurrent userspace writes, but this is benign: the only security-critical invariant is that each field's validated value is the same one used, which local caching guarantees.

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-2026-53250"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-367"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-06-25T09:16:42Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nxsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata()\n\nThe TX metadata area resides in the UMEM buffer which is memory-mapped\nand concurrently writable by userspace. In xsk_skb_metadata(),\ncsum_start and csum_offset are read from shared memory for bounds\nvalidation, then read again for skb assignment. A malicious userspace\napplication can race to overwrite these values between the two reads,\nbypassing the bounds check and causing out-of-bounds memory access\nduring checksum computation in the transmit path.\n\nFix this by reading csum_start and csum_offset into local variables\nonce, then using the local copies for both validation and assignment.\n\nNote that other metadata fields (flags, launch_time) and the cached\ncsum fields may be mutually inconsistent due to concurrent userspace\nwrites, but this is benign: the only security-critical invariant is\nthat each field\u0027s validated value is the same one used, which local\ncaching guarantees.",
  "id": "GHSA-cx83-hxfr-m85v",
  "modified": "2026-09-14T12:31:30Z",
  "published": "2026-06-25T09:31:22Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53250"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0dfe05b938435892875e07771170051346412df9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/22ba97ea9cc1f63a0d0244fae38057ed452b6ac7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bfdfd2706d5fb2cd496a1506e680daf979309c8b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/eb778aed8a9b2381668fcb1247ae4fa011224768"
    }
  ],
  "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-2026-53250 (GCVE-0-2026-53250)

Vulnerability from cvelistv5 – Published: 2026-06-25 08:39 – Updated: 2026-09-14 11:58

Title

xsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata()

Summary

In the Linux kernel, the following vulnerability has been resolved: xsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata() The TX metadata area resides in the UMEM buffer which is memory-mapped and concurrently writable by userspace. In xsk_skb_metadata(), csum_start and csum_offset are read from shared memory for bounds validation, then read again for skb assignment. A malicious userspace application can race to overwrite these values between the two reads, bypassing the bounds check and causing out-of-bounds memory access during checksum computation in the transmit path. Fix this by reading csum_start and csum_offset into local variables once, then using the local copies for both validation and assignment. Note that other metadata fields (flags, launch_time) and the cached csum fields may be mutually inconsistent due to concurrent userspace writes, but this is benign: the only security-critical invariant is that each field's validated value is the same one used, which local caching guarantees.

Severity

7.8 (High)


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

Assigner

Linux mitre root

References

4 references

URL	Tags
https://git.kernel.org/stable/c/eb778aed8a9b23816…
https://git.kernel.org/stable/c/0dfe05b9384358928…
https://git.kernel.org/stable/c/bfdfd2706d5fb2cd4…
https://git.kernel.org/stable/c/22ba97ea9cc1f63a0…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 48eb03dd26304c24f03bdbb9382e89c8564e71df , < eb778aed8a9b2381668fcb1247ae4fa011224768 (git) Affected: 48eb03dd26304c24f03bdbb9382e89c8564e71df , < 0dfe05b938435892875e07771170051346412df9 (git) Affected: 48eb03dd26304c24f03bdbb9382e89c8564e71df , < bfdfd2706d5fb2cd496a1506e680daf979309c8b (git) Affected: 48eb03dd26304c24f03bdbb9382e89c8564e71df , < 22ba97ea9cc1f63a0d0244fae38057ed452b6ac7 (git)
Linux	Linux	Affected: 6.8 Unaffected: 0 , < 6.8 (semver) Unaffected: 6.12.110 , ≤ 6.12.* (semver) Unaffected: 6.18.36 , ≤ 6.18.* (semver) Unaffected: 7.0.13 , ≤ 7.0.* (semver) Unaffected: 7.1 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/xdp/xsk.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "lessThan": "eb778aed8a9b2381668fcb1247ae4fa011224768",
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              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/xdp/xsk.c"
          ],
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          "vendor": "Linux",
          "versions": [
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              "version": "6.8"
            },
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              "lessThan": "6.8",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
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              "status": "unaffected",
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            },
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              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.36",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "7.0.13",
              "versionType": "semver"
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            {
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              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
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      "cpeApplicability": [
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          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "6.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                },
                {
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                }
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata()\n\nThe TX metadata area resides in the UMEM buffer which is memory-mapped\nand concurrently writable by userspace. In xsk_skb_metadata(),\ncsum_start and csum_offset are read from shared memory for bounds\nvalidation, then read again for skb assignment. A malicious userspace\napplication can race to overwrite these values between the two reads,\nbypassing the bounds check and causing out-of-bounds memory access\nduring checksum computation in the transmit path.\n\nFix this by reading csum_start and csum_offset into local variables\nonce, then using the local copies for both validation and assignment.\n\nNote that other metadata fields (flags, launch_time) and the cached\ncsum fields may be mutually inconsistent due to concurrent userspace\nwrites, but this is benign: the only security-critical invariant is\nthat each field\u0027s validated value is the same one used, which local\ncaching guarantees."
        }
      ],
      "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 path is reached by a local process using AF_XDP socket setup, UMEM registration, TX ring submission, and send/poll-driven transmit; it is not reachable directly from remote network packets.\nAC:L - The attacker controls the UMEM metadata and can trigger TX from the same process, so the TOCTOU race can be created with attacker-controlled concurrent writes.\nPR:L - AF_XDP socket creation requires CAP_NET_RAW in the relevant network namespace, which is attainable by a low-privileged local user in user/network namespace deployments.\nUI:N - No victim action is needed after the attacker has local execution; the attacker sets up the socket, UMEM, metadata, and transmit operation directly.\nS:U - The vulnerability corrupts or reads kernel networking memory within the same kernel security authority; this is standard local kernel attack surface, not a VM or hardware boundary crossing.\nC:H - Racing csum_start/csum_offset can bypass validation and drive out-of-bounds checksum reads in kernel transmit checksum handling, so potential kernel memory disclosure is high.\nI:H - The same unvalidated checksum offsets can cause checksum writes to an attacker-influenced out-of-bounds location relative to skb data, making kernel memory corruption plausible.\nA:H - The out-of-bounds memory access in the kernel transmit path can trigger warnings, faults, or kernel crashes and can be repeatedly exercised by the local attacker."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-14T11:58:33.282Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/0dfe05b938435892875e07771170051346412df9"
        },
        {
          "url": "https://git.kernel.org/stable/c/bfdfd2706d5fb2cd496a1506e680daf979309c8b"
        },
        {
          "url": "https://git.kernel.org/stable/c/22ba97ea9cc1f63a0d0244fae38057ed452b6ac7"
        }
      ],
      "title": "xsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-53250",
    "datePublished": "2026-06-25T08:39:42.630Z",
    "dateReserved": "2026-06-09T07:44:35.394Z",
    "dateUpdated": "2026-09-14T11:58:33.282Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

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.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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