What’s Vulnerable › Vulnerabilities

CVE-2026-74597: ip6_tunnel: clear skb2->cb[] in ip6ip6_err()

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-22 · updated 2026-10-16

Description

In the Linux kernel, the following vulnerability has been resolved: ip6_tunnel: clear skb2->cb[] in ip6ip6_err() ip6ip6_err() clones an outer IPv6 ICMP error skb, pulls it to the quoted inner IPv6 packet, and then passes the clone to icmpv6_send(). The clone still carries the outer packet's inet6_skb_parm in skb->cb. If the outer packet had a Home Address Option, IP6CB(skb2)->dsthao remains non-zero after skb_pull(). icmpv6_send() later calls mip6_addr_swap(), which uses that stale dsthao offset against the quoted inner packet. A malformed inner destination-options header can then make the HAO lookup and address swap run past the end of the quoted packet and corrupt skb_shared_info. Clear skb2->cb[] before pulling the quoted inner IPv6 packet so the reply path does not reuse metadata left by the outer IPv6 stack.

Affected products

• Linux kernel: 2.6.22 — fixed in 7.2

How to fix

Upgrade to a fixed version: Linux kernel 7.2. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/0dadb0620ab65949a8bc2439dd28ea3c942fe87d
• https://git.kernel.org/stable/c/44fe898df302e91c5ee5acbc71ffa74e78e6c183
• https://git.kernel.org/stable/c/484134e1eb07d700a73b1e4bbf3fb503e299be60
• https://git.kernel.org/stable/c/4eb15c465337b18f44716c499cd6ad63eee0ad54
• https://git.kernel.org/stable/c/64e41736a26f37ab6215bc2e6df125df05aceb08
• https://git.kernel.org/stable/c/b6816536a2990c0db44a26130a03e40b441e829b
• https://git.kernel.org/stable/c/f803c086399da277b5d0ff36a107d0f162751800
• https://git.kernel.org/stable/c/fbf40faa0414b753212494ad197542002e66ed9e

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