xfrm: iptfs: fix runt reassembly panic from short inner tot_len

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-98371
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-06 09:18:31 UTC
Updated2026-10-19 10:18:40 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: xfrm: iptfs: fix runt reassembly panic from short inner tot_len When the start of an inner packet is split across two outer packets such that fewer than 4 bytes land at the end of the first one, __input_process_payload() saves those bytes as a runt and skips the iplen/iphlen validation performed for in-place packets. When the continuation packet arrives, iptfs_reassem_cont() only requires the declared inner length to be >= sizeof(ra_runt) (6) before allocating the reassembly skb with that attacker-controlled length. However, __iptfs_iphlen() always returns the fixed minimum IP header size (20 for IPv4, 40 for IPv6), so for an inner IPv4 tot_len in [6, 19] the header-completion copy writes past the declared packet length, and the subsequent "ipremain -= copylen" underflows to ~4GB, leaving the payload copy length bounded only by blkoff (up to 64KB). At runtime the skb_put() tailroom check turns this into skb_over_panic(), i.e. an unprivileged kernel panic (DoS), reachable locally via userns+netns IPTFS SAs and remotely against IPTFS VPN gateways when the decrypted outer skb is linear (e.g. AF_PACKET taps, tun/tap delivery). Align the runt path with the normal path by requiring the declared inner length to cover at least the IP header size. This also subsumes the previous >= sizeof(ra_runt) check, since the minimum IP header is always larger than the runt buffer. This issue was found by the autokbug dynamic kernel fuzzer at Tencent Yunding Lab.

Risk And Classification

EPSS: 0.001610000 probability, percentile 0.047060000 (date 2026-10-06)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 07569476544681816335099929ff3494dfbf6b05 a7018ee0ea8622ed59edc064be4e0f2c26464f53 git Not specified
CNA Linux Linux affected 07569476544681816335099929ff3494dfbf6b05 5b8afb56ccb7c014b0f1ac40341708b200443c2d git Not specified
CNA Linux Linux affected 07569476544681816335099929ff3494dfbf6b05 dc33262be1fe43d0eb0b84fb58c6ed42e2f64a8c git Not specified
CNA Linux Linux affected 6.14 Not specified
CNA Linux Linux unaffected 6.14 semver Not specified
CNA Linux Linux unaffected 6.18.54 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.8 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/a7018ee0ea8622ed59edc064be4e0f2c26464f53 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/dc33262be1fe43d0eb0b84fb58c6ed42e2f64a8c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/5b8afb56ccb7c014b0f1ac40341708b200443c2d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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