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CVE-2026-89563

ip6_tunnel: use skb_cow_head() in ip6_tnl_xmit()

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

Summary

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().

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 058214a4d1dfefed9f01a277fadd3590acb5f990 · fixed in 6e8eff8ed13b14708bc39f170144eacde494aac6; From 058214a4d1dfefed9f01a277fadd3590acb5f990 · fixed in dc1a319a4815c074914e2812e0e9cd0164ca682b; From 058214a4d1dfefed9f01a277fadd3590acb5f990 · fixed in 629d5557e635cdbc109a14ed913ba5a540e3f79a; From 058214a4d1dfefed9f01a277fadd3590acb5f990 · fixed in defa0adeff132cc90ed66915b9a104d9393e1e54; From 058214a4d1dfefed9f01a277fadd3590acb5f990 · fixed in 37df5bc6b5ccad88c2faa0f5466f150178882b74; From 058214a4d1dfefed9f01a277fadd3590acb5f990 · fixed in b36dfd6e8cff00cea81c11cc0af88d1564763461; From 058214a4d1dfefed9f01a277fadd3590acb5f990 · fixed in 8fc56ca49fc0ee1725b55c67bb43ab0dd01f3f52; From 058214a4d1dfefed9f01a277fadd3590acb5f990 · fixed in 87f21b59ddc618eff9670c174842964ad65fdade

  • Linux Linux

    4.7

  • KernelLinux

    From 4.7.0 · fixed in 5.10.270; From 5.11.0 · fixed in 5.15.221; From 5.16.0 · fixed in 6.1.188; From 6.2.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.109; From 6.13.0 · fixed in 6.18.50; From 6.19.0 · fixed in 7.2.4

References 8

git.kernel.org