CVE-2026-53250 (GCVE-0-2026-53250)
Vulnerability from cvelistv5
Published
2026-06-25 08:39
Modified
2026-08-05 12:34
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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.
References
Impacted products
Vendor Product Version
Linux Linux Version: 48eb03dd26304c24f03bdbb9382e89c8564e71df
Version: 48eb03dd26304c24f03bdbb9382e89c8564e71df
Version: 48eb03dd26304c24f03bdbb9382e89c8564e71df
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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": "0dfe05b938435892875e07771170051346412df9",
              "status": "affected",
              "version": "48eb03dd26304c24f03bdbb9382e89c8564e71df",
              "versionType": "git"
            },
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              "versionType": "git"
            },
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              "status": "affected",
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              "versionType": "git"
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          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/xdp/xsk.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.8"
            },
            {
              "lessThan": "6.8",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.36",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.13",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.36",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
                },
                {
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                  "versionEndExcluding": "7.0.13",
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                  "vulnerable": true
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                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "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": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "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": "2026-08-05T12:34:33.657Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "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": "2026-08-05T12:34:33.657Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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