CVE-2026-74478 (GCVE-0-2026-74478)

Vulnerability from cvelistv5 – Published: 2026-08-15 12:27 – Updated: 2026-08-17 05:47
VLAI
Title
um: vector: fix use-after-free in vector_mmsg_rx()
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.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb , < 4b9601595e8b6b5d18878cac0aeabc687d241111 (git)
Affected: 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb , < 67d58ab4f2ccf7145f3da07e025735a09c79de1b (git)
Affected: 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb , < 180ff4c81faf01ec4e06082c9daa7c40518ead89 (git)
Affected: 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb , < 804b681002ead233abf49a3efd681f5468a835f9 (git)
Affected: 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb , < af421e9aed3920c7ac88c24daa48606c7112feca (git)
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Linux Linux Affected: 4.17
Unaffected: 0 , < 4.17 (semver)
Unaffected: 6.6.151 , ≤ 6.6.* (semver)
Unaffected: 6.12.103 , ≤ 6.12.* (semver)
Unaffected: 6.18.44 , ≤ 6.18.* (semver)
Unaffected: 7.1.8 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
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          "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."
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        {
          "url": "https://git.kernel.org/stable/c/af421e9aed3920c7ac88c24daa48606c7112feca"
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    "datePublished": "2026-08-15T12:27:12.549Z",
    "dateReserved": "2026-08-15T05:44:03.903Z",
    "dateUpdated": "2026-08-17T05:47:38.560Z",
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    "suse_vex": {
      "aggregate_severity": "critical",
      "current_release_date": "2026-08-17T16:26:37Z",
      "cve": "CVE-2026-74478",
      "id": "CVE-2026-74478",
      "initial_release_date": "2026-08-15T23:52:08Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-74478",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-74478.json",
      "version": "3"
    }
  }
}



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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

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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.