CVE-2026-98371 is a vulnerability in Linux Kernel
Published on October 6, 2026
xfrm: iptfs: fix runt reassembly panic from short inner tot_len
In 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.
Products Associated with CVE-2026-98371
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Affected Versions
Linux:- Version 07569476544681816335099929ff3494dfbf6b05 and below a7018ee0ea8622ed59edc064be4e0f2c26464f53 is affected.
- Version 07569476544681816335099929ff3494dfbf6b05 and below 5b8afb56ccb7c014b0f1ac40341708b200443c2d is affected.
- Version 07569476544681816335099929ff3494dfbf6b05 and below dc33262be1fe43d0eb0b84fb58c6ed42e2f64a8c is affected.
- Version 6.14 is affected.
- Before 6.14 is unaffected.
- Version 6.18.54, <= 6.18.* is unaffected.
- Version 7.2.8, <= 7.2.* is unaffected.
- Version 7.3-rc4, <= * is unaffected.