net: fix skb length accounting after generic XDP frag adjustment

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Summary

CVECVE-2026-74665
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-22 16:16:40 UTC
Updated2026-08-22 16:16:40 UTC
DescriptionIn 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.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected e6d5dbdd20aa6a86974af51deb9414cd2e7794cb 72468efcc089782fa047afddd10856b11a14ef5b git Not specified
CNA Linux Linux affected e6d5dbdd20aa6a86974af51deb9414cd2e7794cb 5f30f9c302cea1f2ebf97abe574c1826544223d7 git Not specified
CNA Linux Linux affected e6d5dbdd20aa6a86974af51deb9414cd2e7794cb ea1ccd6d1c6370868e3b032a3fc575b9c397f2e1 git Not specified
CNA Linux Linux affected e6d5dbdd20aa6a86974af51deb9414cd2e7794cb 33f2b2eb33d666ecac68031e0f31424fb70528db git Not specified
CNA Linux Linux affected 6.9 Not specified
CNA Linux Linux unaffected 6.9 semver Not specified
CNA Linux Linux unaffected 6.12.104 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.45 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.9 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/33f2b2eb33d666ecac68031e0f31424fb70528db 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/5f30f9c302cea1f2ebf97abe574c1826544223d7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/72468efcc089782fa047afddd10856b11a14ef5b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ea1ccd6d1c6370868e3b032a3fc575b9c397f2e1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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