CVE Catalog

CVE-2026-98371

Unknown
Published: Translated: NVD NIST

Summary

In the Linux kernel, a flaw in xfrm/iptfs handling of inner packet fragmentation occurs 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. This bypasses IP header length validation, leading to a buffer overflow and kernel panic (DoS).

Risk Assessment

An unprivileged local user can trigger a kernel panic via userns+netns IPTFS SAs, and a remote attacker can do so against IPTFS VPN gateways when the decrypted outer skb is linear (e.g., AF_PACKET taps, tun/tap delivery). This results in system unavailability (DoS).

Recommendation

Update the Linux kernel to a version containing the fix that requires the declared inner packet length to cover at least the IP header size. If immediate update is not possible, restrict access to IPTFS interfaces and consider disabling unused xfrm/iptfs features.

Other vulnerabilities in Linux kernel

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Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS