CriticalFix available

um: vector: fix use-after-free in vector_mmsg_rx()

Type: advisorySources: OSV

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.

Products: Kernel
Affected versions: Not specified
Fixed versions: 5.10.265, 5.15.216, 6.1.183, 6.12.103, 6.18.44, 6.6.151, 7.1.8
CVEs: CVE-2026-74478
Confirmed fixed CVEs: Not specified
Updated in this feed: 3 Nov 2026, 11:32 UTC · Revision 1

Source evidence

um: vector: fix use-after-free in vector_mmsg_rx()

core-osv · Original source

Published 15 Aug 2026, 12:27 UTC

osv:CVE-2026-74478

Kernel

Fixed versions: 5.10.265, 5.15.216, 6.1.183, 6.6.151, 6.12.103, 6.18.44, 7.1.8

Complete source record

{
  "id": "9041e6463578cca266bc1aeb7657582a38f5b6a546edb112cc1d42eb10ed1698",
  "url": "https://osv.dev/vulnerability/CVE-2026-74478",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "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.",
    "evidence": "osv:CVE-2026-74478",
    "products": [
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      "modified": "2026-10-28T02:30:28.266261736Z",
      "provider": "osv",
      "references": [
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        "https://git.kernel.org/stable/c/4b9601595e8b6b5d18878cac0aeabc687d241111",
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        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74478.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-74478",
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      "provider_metadata": {
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        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74478.json"
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    },
    "related_cves": [
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
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  "source_id": "core-osv",
  "document_id": 494991,
  "published_at": "2026-08-15T12:27:12.549+00:00"
}