CVE-2026-74665 (GCVE-0-2026-74665)

Vulnerability from cvelistv5 – Published: 2026-08-22 15:32 – Updated: 2026-08-25 05:41
VLAI
Title
net: fix skb length accounting after generic XDP frag adjustment
Summary
In the Linux kernel, the following vulnerability has been resolved: net: fix skb length accounting after generic XDP frag adjustment Generic XDP exposes non-linear skb fragments through an xdp_buff. If an XDP program adjusts the fragment area, bpf_prog_run_generic_xdp() copies xdp_frags_size back to skb->data_len but leaves skb->len containing the old fragment contribution. After a fragment shrink, this makes skb_headlen() larger than the actual linear area. In the reproduced UDP receive path, __skb_datagram_iter() copied 1024 bytes past the actual linear tail to userspace, starting at struct skb_shared_info. The copied bytes included the affected skb's nr_frags, xdp_frags_size and a kernel pointer from skb_shinfo(skb)->frags[0]. Real packet data was displaced by the same amount and truncated at the end. Subtract the old data_len before replacing it and add the new data_len afterwards, keeping skb->len and skb->data_len synchronized. A 60000-byte UDP datagram on a veth pair with MTU 64000 was shortened by 1024 bytes from its fragment area. Before the fix, all 10 runs produced corrupted payloads. After the fix, all 10 runs matched the expected payload exactly.
Severity
9.1 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: e6d5dbdd20aa6a86974af51deb9414cd2e7794cb , < 72468efcc089782fa047afddd10856b11a14ef5b (git)
Affected: e6d5dbdd20aa6a86974af51deb9414cd2e7794cb , < 5f30f9c302cea1f2ebf97abe574c1826544223d7 (git)
Affected: e6d5dbdd20aa6a86974af51deb9414cd2e7794cb , < ea1ccd6d1c6370868e3b032a3fc575b9c397f2e1 (git)
Affected: e6d5dbdd20aa6a86974af51deb9414cd2e7794cb , < 33f2b2eb33d666ecac68031e0f31424fb70528db (git)
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Linux Linux Affected: 6.9
Unaffected: 0 , < 6.9 (semver)
Unaffected: 6.12.104 , ≤ 6.12.* (semver)
Unaffected: 6.18.45 , ≤ 6.18.* (semver)
Unaffected: 7.1.9 , ≤ 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\nnet: fix skb length accounting after generic XDP frag adjustment\n\nGeneric XDP exposes non-linear skb fragments through an xdp_buff. If an\nXDP program adjusts the fragment area, bpf_prog_run_generic_xdp() copies\nxdp_frags_size back to skb-\u003edata_len but leaves skb-\u003elen containing the\nold fragment contribution.\n\nAfter a fragment shrink, this makes skb_headlen() larger than the actual\nlinear area. In the reproduced UDP receive path, __skb_datagram_iter()\ncopied 1024 bytes past the actual linear tail to userspace, starting at\nstruct skb_shared_info. The copied bytes included the affected skb\u0027s\nnr_frags, xdp_frags_size and a kernel pointer from\nskb_shinfo(skb)-\u003efrags[0]. Real packet data was displaced by the same\namount and truncated at the end.\n\nSubtract the old data_len before replacing it and add the new data_len\nafterwards, keeping skb-\u003elen and skb-\u003edata_len synchronized.\n\nA 60000-byte UDP datagram on a veth pair with MTU 64000 was shortened by\n1024 bytes from its fragment area. Before the fix, all 10 runs produced\ncorrupted payloads. After the fix, all 10 runs matched the expected\npayload exactly."
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              "value": "AV:N - The flaw is hit when remotely delivered packets traverse __netif_receive_skb_core(), netif_receive_generic_xdp(), and bpf_prog_run_generic_xdp() on any netdev with generic XDP (SKB mode) attached, matching the reproduced UDP receive path on a veth pair.\nAC:L - An attacker can reliably send large fragmented datagrams (reproducer used a 60000-byte UDP payload) to create a nonlinear skb and drive bpf_xdp_adjust_tail() fragment shrink before XDP_PASS, with no race or conditions outside attacker packet control.\nPR:N - Exploitation only requires generic XDP using bpf_xdp_adjust_tail to already be attached on a reachable interface; the remote packet sender needs no local account, capabilities, or authentication to trigger the bad skb length accounting.\nUI:N - No victim interaction is needed beyond normal always-on packet reception and socket delivery; corrupted/leaked data is produced automatically when a userspace process reads the affected datagram.\nS:U - Impact stays within the same kernel/host security authority by leaking kernel memory into a local userspace receive buffer and does not by itself cross VM, container, or IOMMU isolation boundaries.\nC:H - Inflated skb_headlen() makes __skb_datagram_iter() copy up to 1024 bytes past the real linear tail into userspace, exposing skb_shared_info metadata and a kernel pointer from skb_shinfo(skb)-\u003efrags[0].\nI:H - The same length mismatch displaces and truncates real packet bytes in the delivered datagram, corrupting application-visible data beyond intended bounds and compounding misuse of leaked kernel metadata.\nA:N - The demonstrated failure is out-of-bounds kernel-to-userspace copy and datagram corruption without a reported kernel panic, oops, hang, or other availability loss in the fix commit or reproduction."
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        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/33f2b2eb33d666ecac68031e0f31424fb70528db"
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    "datePublished": "2026-08-22T15:32:37.346Z",
    "dateReserved": "2026-08-15T05:44:03.924Z",
    "dateUpdated": "2026-08-25T05:41:19.196Z",
    "state": "PUBLISHED"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-25T08:53:40+00:00",
      "cve": "CVE-2026-74665",
      "id": "CVE-2026-74665",
      "initial_release_date": "2026-08-22T00:00:00+00:00",
      "product_status:known_affected": "90",
      "product_status:known_not_affected": "184",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net: fix skb length accounting after generic XDP frag adjustment",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74665.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.