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CVE-2026-43037

ip6_tunnel: clear skb2->cb[] in ip4ip6_err()

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: total

Summary

In the Linux kernel, the following vulnerability has been resolved: ip6_tunnel: clear skb2->cb[] in ip4ip6_err() Oskar Kjos reported the following problem. ip4ip6_err() calls icmp_send() on a cloned skb whose cb[] was written by the IPv6 receive path as struct inet6_skb_parm. icmp_send() passes IPCB(skb2) to __ip_options_echo(), which interprets that cb[] region as struct inet_skb_parm (IPv4). The layouts differ: inet6_skb_parm.nhoff at offset 14 overlaps inet_skb_parm.opt.rr, producing a non-zero rr value. __ip_options_echo() then reads optlen from attacker-controlled packet data at sptr[rr+1] and copies that many bytes into dopt->__data, a fixed 40-byte stack buffer (IP_OPTIONS_DATA_FIXED_SIZE). To fix this we clear skb2->cb[], as suggested by Oskar Kjos. Also add minimal IPv4 header validation (version == 4, ihl >= 5).

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From c4d3efafcc933fd2ffd169d7dc4f980393a13796 · fixed in ea9f65b27c8404e164848ebff1443310fd187629; From c4d3efafcc933fd2ffd169d7dc4f980393a13796 · fixed in d6621f60192fe10c047a4487be42a6f4c150707f; From c4d3efafcc933fd2ffd169d7dc4f980393a13796 · fixed in 2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5; From c4d3efafcc933fd2ffd169d7dc4f980393a13796 · fixed in a0c4ce9900a108eaf55d0f3b399cb55999647d39; From c4d3efafcc933fd2ffd169d7dc4f980393a13796 · fixed in 1063515ce15ff31065c4e7f8265f4c2fd3c54876; From c4d3efafcc933fd2ffd169d7dc4f980393a13796 · fixed in 590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3; From c4d3efafcc933fd2ffd169d7dc4f980393a13796 · fixed in 4a622658f384b03560834cbe8ffcfe69a278f7c8; From c4d3efafcc933fd2ffd169d7dc4f980393a13796 · fixed in 2edfa31769a4add828a7e604b21cb82aaaa05925

  • Linux Linux

    2.6.22

  • KernelLinux

    From 2.6.22 · fixed in 5.10.253; From 5.11.0 · fixed in 5.15.203; From 5.16.0 · fixed in 6.1.168; From 6.2.0 · fixed in 6.6.134; From 6.7.0 · fixed in 6.12.81; From 6.13.0 · fixed in 6.18.22; From 6.19.0 · fixed in 6.19.12

References 8

git.kernel.org