GHSA-PG5F-GW23-248R
Vulnerability from github – Published: 2026-08-22 18:30 – Updated: 2026-08-25 06:31In the Linux kernel, the following vulnerability has been resolved:
veth: fix skb length accounting after XDP frag adjustment
veth exposes non-linear skb fragments through an xdp_buff. If an XDP program adjusts the fragment area, veth_xdp_rcv_skb() 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.
Additionally, bpf_xdp_pull_data() can advance data_end while leaving frags present. The skb is then still non-linear, so the old __skb_put(skb, off) triggers SKB_LINEAR_ASSERT().
Use skb_set_tail_pointer() and update skb->len explicitly instead, following bpf_prog_run_generic_xdp(). Unlike __skb_put(), skb_set_tail_pointer() does not require a linear skb.
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. A forced-tailroom reproducer also exercises bpf_xdp_pull_data() with frags still present; the old code triggers SKB_LINEAR_ASSERT(), while this fix passes 10/10 runs.
{
"affected": [],
"aliases": [
"CVE-2026-74612"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-22T16:16:33Z",
"severity": "CRITICAL"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nveth: fix skb length accounting after XDP frag adjustment\n\nveth exposes non-linear skb fragments through an xdp_buff. If an XDP\nprogram adjusts the fragment area, veth_xdp_rcv_skb() 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\nAdditionally, bpf_xdp_pull_data() can advance data_end while leaving\nfrags present. The skb is then still non-linear, so the old\n__skb_put(skb, off) triggers SKB_LINEAR_ASSERT().\n\nUse skb_set_tail_pointer() and update skb-\u003elen explicitly instead,\nfollowing bpf_prog_run_generic_xdp(). Unlike __skb_put(),\nskb_set_tail_pointer() does not require a linear skb.\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. A forced-tailroom reproducer also exercises\nbpf_xdp_pull_data() with frags still present; the old code triggers\nSKB_LINEAR_ASSERT(), while this fix passes 10/10 runs.",
"id": "GHSA-pg5f-gw23-248r",
"modified": "2026-08-25T06:31:22Z",
"published": "2026-08-22T18:30:26Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74612"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0c3024afabb8064b141f3cedcb1ddd6ab05ad9d5"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2f2a7f3f8b9f1bffc9b0488aa02b6951b2aec139"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3205b0652a37255dbb7ca8f3d942c8d8aa677c21"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/41b96667d42b74bb4b137f1bb78b611a953c5943"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cb6379feaaff11c4e1e79c26c745ffa23182768a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cdf745b7a777f87f51666e5d8f4c6fc279bcf54d"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Confirmed: The vulnerability has been validated from an analyst's perspective.
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- 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.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.