FKIE_CVE-2026-74478

Vulnerability from fkie_nvd - Published: 2026-08-15 13:17 - Updated: 2026-08-19 17:21
Severity
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: um: vector: fix use-after-free in vector_mmsg_rx() When vector_mmsg_rx() discards a packet whose overlay header fails verify_header(), it frees the skb and continues the loop: if (header_check < 0) { dev_kfree_skb_irq(skb); vp->estats.rx_encaps_errors++; continue; } The normal and short-packet paths fall through to the bottom of the loop body, which clears the consumed slot and advances the cursors: (*skbuff_vector) = NULL; mmsg_vector++; skbuff_vector++; The verify_header() < 0 path skips that via continue, so the freed skb is left in skbuff_vector[] and the cursors do not advance. The next iteration reads the same slot, gets the freed skb, and frees it again, producing a refcount underflow / use-after-free in the RX path. Discard the slot the same way the other paths do before continuing. Only transports whose verify_header() can return negative are affected: GRE and L2TPv3 do so on a cookie/session-id mismatch (raw/tap do not), so any peer on such a transport can trigger it without authentication.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/180ff4c81faf01ec4e06082c9daa7c40518ead89
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/4b9601595e8b6b5d18878cac0aeabc687d241111
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/67d58ab4f2ccf7145f3da07e025735a09c79de1b
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7dc9781e320d664c9bdd50003c9acfddf363d1e1
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/804b681002ead233abf49a3efd681f5468a835f9
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/967c779c9853d2a1cc9cd8e61d300250c348f3d9
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a7bc015bb798c525e7a82dd14225c6aeb994274b
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/af421e9aed3920c7ac88c24daa48606c7112feca
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/um/drivers/vector_kern.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "967c779c9853d2a1cc9cd8e61d300250c348f3d9",
              "status": "affected",
              "version": "49da7e64f33e80edffb1a9eeb230fa4c3f42dffb",
              "versionType": "git"
            },
            {
              "lessThan": "a7bc015bb798c525e7a82dd14225c6aeb994274b",
              "status": "affected",
              "version": "49da7e64f33e80edffb1a9eeb230fa4c3f42dffb",
              "versionType": "git"
            },
            {
              "lessThan": "7dc9781e320d664c9bdd50003c9acfddf363d1e1",
              "status": "affected",
              "version": "49da7e64f33e80edffb1a9eeb230fa4c3f42dffb",
              "versionType": "git"
            },
            {
              "lessThan": "4b9601595e8b6b5d18878cac0aeabc687d241111",
              "status": "affected",
              "version": "49da7e64f33e80edffb1a9eeb230fa4c3f42dffb",
              "versionType": "git"
            },
            {
              "lessThan": "67d58ab4f2ccf7145f3da07e025735a09c79de1b",
              "status": "affected",
              "version": "49da7e64f33e80edffb1a9eeb230fa4c3f42dffb",
              "versionType": "git"
            },
            {
              "lessThan": "180ff4c81faf01ec4e06082c9daa7c40518ead89",
              "status": "affected",
              "version": "49da7e64f33e80edffb1a9eeb230fa4c3f42dffb",
              "versionType": "git"
            },
            {
              "lessThan": "804b681002ead233abf49a3efd681f5468a835f9",
              "status": "affected",
              "version": "49da7e64f33e80edffb1a9eeb230fa4c3f42dffb",
              "versionType": "git"
            },
            {
              "lessThan": "af421e9aed3920c7ac88c24daa48606c7112feca",
              "status": "affected",
              "version": "49da7e64f33e80edffb1a9eeb230fa4c3f42dffb",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "arch/um/drivers/vector_kern.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.17"
            },
            {
              "lessThan": "4.17",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.265",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.216",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.183",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.151",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.103",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.44",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\num: vector: fix use-after-free in vector_mmsg_rx()\n\nWhen vector_mmsg_rx() discards a packet whose overlay header fails\nverify_header(), it frees the skb and continues the loop:\n\n\tif (header_check \u003c 0) {\n\t\tdev_kfree_skb_irq(skb);\n\t\tvp-\u003eestats.rx_encaps_errors++;\n\t\tcontinue;\n\t}\n\nThe normal and short-packet paths fall through to the bottom of the\nloop body, which clears the consumed slot and advances the cursors:\n\n\t(*skbuff_vector) = NULL;\n\tmmsg_vector++;\n\tskbuff_vector++;\n\nThe verify_header() \u003c 0 path skips that via continue, so the freed skb\nis left in skbuff_vector[] and the cursors do not advance. The next\niteration reads the same slot, gets the freed skb, and frees it again,\nproducing a refcount underflow / use-after-free in the RX path.\n\nDiscard the slot the same way the other paths do before continuing.\n\nOnly transports whose verify_header() can return negative are affected:\nGRE and L2TPv3 do so on a cookie/session-id mismatch (raw/tap do not),\nso any peer on such a transport can trigger it without authentication."
    }
  ],
  "id": "CVE-2026-74478",
  "lastModified": "2026-08-19T17:21:04.947",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-08-15T13:17:52.600",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/180ff4c81faf01ec4e06082c9daa7c40518ead89"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/4b9601595e8b6b5d18878cac0aeabc687d241111"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/67d58ab4f2ccf7145f3da07e025735a09c79de1b"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/7dc9781e320d664c9bdd50003c9acfddf363d1e1"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/804b681002ead233abf49a3efd681f5468a835f9"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/967c779c9853d2a1cc9cd8e61d300250c348f3d9"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a7bc015bb798c525e7a82dd14225c6aeb994274b"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/af421e9aed3920c7ac88c24daa48606c7112feca"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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