CVE-2026-98096

Summary

In the Linux kernel, the following vulnerability has been resolved:

ipv6: sr: restore network header before routing and forwarding

ipv6_srh_rcv() runs with skb->data at the Segment Routing Header (SRH) while skb_network_header() points at the IPv6 header.

When segments_left > 0, ipv6_srh_rcv() previously restored the skb->data position by pushing sizeof(struct ipv6hdr), assuming the SRH immediately followed the fixed IPv6 header. If another extension header (such as a Hop-by-Hop options header) precedes the SRH, skb_network_offset() remained negative.

This led to two problems:

1. During ip6_route_input(), fib6_rules_early_flow_dissect() invokes __skb_flow_dissect() which passes the negative skb_network_offset() to flow dissection, breaking BPF and C flow dissector logic.
2. If forwarded via ip6_forward() or redirected via act_mirred, downstream handlers (like sch_fragment() or neighbour output) pass the negative offset as an unsigned length, triggering OOB memcpy or buffer overflows.

Fix this by pushing -skb_network_offset(skb) before routing, ensuring skb_network_offset(skb) is 0 for route lookup / flow dissection as well as downstream forwarding. On the loopback path, pull skb_transport_offset(skb) to restore skb->data to the SRH before looping back.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/ce4c8beedc19aceeab0e7bdc6f34394fb158c47c
• https://git.kernel.org/stable/c/97b21ef57dfabbff660a4672c9fef7edfb720f47
• https://git.kernel.org/stable/c/3ad7dca5e03bd64c65983a19734337512fd75491
• https://git.kernel.org/stable/c/975b5b067f525a1b1338c4a3bee1c46545801518

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