CVE-2026-89563

In the Linux kernel, the following vulnerability has been resolved: ip6_tunnel: use skb_cow_head() in ip6_tnl_xmit() ip6_tnl_xmit() may need to expand headroom before it can push the outer IPv6 and optional encap headers. It currently does that with skb_realloc_headroom(), copies skb->sk ownership, consumes the original skb, and then continues processing with the replacement skb kept only in its local variable. That is safe only if the helper cannot fail afterwards. But this helper still has post-reallocation error exits. collect_md tunnels reject non-NONE encap after the replacement, and ip6_tnl_encap() can also fail later. In those cases the helper returns an error to its callers while the caller still only has the original skb pointer. Both ip6_tnl_start_xmit() and the IPv6 GRE paths free the caller skb on error, so they can end up freeing an skb that ip6_tnl_xmit() already consumed. Use skb_cow_head() instead. It provides the required headroom and writability without privately replacing the caller-owned skb, so later error returns cannot leave callers with a stale pointer. The Ethernet users, ip6gretap and ip6erspan, clear IFF_TX_SKB_SHARING and already call skb_cow_head() before entering ip6_tnl_xmit(). They do not rely on the removed skb_shared() reallocation. This also makes the IPv6 tunnel path consistent with ip_tunnel_xmit().

• https://git.kernel.org/stable/c/37df5bc6b5ccad88c2faa0f5466f150178882b74
• https://git.kernel.org/stable/c/629d5557e635cdbc109a14ed913ba5a540e3f79a
• https://git.kernel.org/stable/c/6e8eff8ed13b14708bc39f170144eacde494aac6
• https://git.kernel.org/stable/c/87f21b59ddc618eff9670c174842964ad65fdade
• https://git.kernel.org/stable/c/8fc56ca49fc0ee1725b55c67bb43ab0dd01f3f52
• https://git.kernel.org/stable/c/b36dfd6e8cff00cea81c11cc0af88d1564763461
• https://git.kernel.org/stable/c/dc1a319a4815c074914e2812e0e9cd0164ca682b
• https://git.kernel.org/stable/c/defa0adeff132cc90ed66915b9a104d9393e1e54

Published

Sep 11, 2026

Last Modified

Sep 14, 2026

Status

Received

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2026-89558In the Linux kernel, the following vulnerability has been re…9.8
• CVE-2026-89559In the Linux kernel, the following vulnerability has been re…7.8
• CVE-2026-8956Integer overflow in the Networking: JAR component. This vuln…9.8
• CVE-2026-89560In the Linux kernel, the following vulnerability has been re…8.4
• CVE-2026-89561In the Linux kernel, the following vulnerability has been re…7.5
• CVE-2026-89562In the Linux kernel, the following vulnerability has been re…7.8
• CVE-2026-89564In the Linux kernel, the following vulnerability has been re…7.8
• CVE-2026-89565In the Linux kernel, the following vulnerability has been re…
• CVE-2026-89566In the Linux kernel, the following vulnerability has been re…
• CVE-2026-89567In the Linux kernel, the following vulnerability has been re…
• CVE-2026-89568In the Linux kernel, the following vulnerability has been re…
• CVE-2026-89569In the Linux kernel, the following vulnerability has been re…8.8