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CVE PROGRAM SOURCE RECORD9.8 Critical

CVE-2026-43037

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

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Status
Published
Published
Updated
Assigning organization
Linux

Description

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).

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • c4d3efafcc933fd2ffd169d7dc4f980393a13796 to < ea9f65b27c8404e164848ebff1443310fd187629affected
  • c4d3efafcc933fd2ffd169d7dc4f980393a13796 to < d6621f60192fe10c047a4487be42a6f4c150707faffected
  • c4d3efafcc933fd2ffd169d7dc4f980393a13796 to < 2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5affected
  • c4d3efafcc933fd2ffd169d7dc4f980393a13796 to < a0c4ce9900a108eaf55d0f3b399cb55999647d39affected
  • c4d3efafcc933fd2ffd169d7dc4f980393a13796 to < 1063515ce15ff31065c4e7f8265f4c2fd3c54876affected
  • c4d3efafcc933fd2ffd169d7dc4f980393a13796 to < 590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3affected
  • c4d3efafcc933fd2ffd169d7dc4f980393a13796 to < 4a622658f384b03560834cbe8ffcfe69a278f7c8affected
  • c4d3efafcc933fd2ffd169d7dc4f980393a13796 to < 2edfa31769a4add828a7e604b21cb82aaaa05925affected

Linux Linux

Default version status: affected

  • 2.6.22affected
  • 0 to < 2.6.22unaffected
  • 5.10.253 to ≤ 5.10.*unaffected
  • 5.15.203 to ≤ 5.15.*unaffected
  • 6.1.168 to ≤ 6.1.*unaffected
  • 6.6.134 to ≤ 6.6.*unaffected
  • 6.12.81 to ≤ 6.12.*unaffected
  • 6.18.22 to ≤ 6.18.*unaffected
  • 6.19.12 to ≤ 6.19.*unaffected
  • 7.0 to ≤ *unaffected

References