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CVE-2026-43038

ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach()

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: ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach() Sashiko AI-review observed: In ip6_err_gen_icmpv6_unreach(), the skb is an outer IPv4 ICMP error packet where its cb contains an IPv4 inet_skb_parm. When skb is cloned into skb2 and passed to icmp6_send(), it uses IP6CB(skb2). IP6CB interprets the IPv4 inet_skb_parm as an inet6_skb_parm. The cipso offset in inet_skb_parm.opt directly overlaps with dsthao in inet6_skb_parm at offset 18. If an attacker sends a forged ICMPv4 error with a CIPSO IP option, dsthao would be a non-zero offset. Inside icmp6_send(), mip6_addr_swap() is called and uses ipv6_find_tlv(skb, opt->dsthao, IPV6_TLV_HAO). This would scan the inner, attacker-controlled IPv6 packet starting at that offset, potentially returning a fake TLV without checking if the remaining packet length can hold the full 18-byte struct ipv6_destopt_hao. Could mip6_addr_swap() then perform a 16-byte swap that extends past the end of the packet data into skb_shared_info? Should the cb array also be cleared in ip6_err_gen_icmpv6_unreach() and ip6ip6_err() to prevent this? This patch implements the first suggestion. I am not sure if ip6ip6_err() needs to be changed. A separate patch would be better anyway.

Timeline

  1. CVE published
  2. CISA SSVC assessment

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

  3. Record last updated

Affected versions

  • Linux Linux

    From ca15a078bd907df5fc1c009477869c5cbde3b753 · fixed in c438ba010171b70bad22fc18b1d5bdc3627476e8; From ca15a078bd907df5fc1c009477869c5cbde3b753 · fixed in 0452b6526b2f54b2413b9cb4ff1ea2ac542c99c7; From ca15a078bd907df5fc1c009477869c5cbde3b753 · fixed in a4437faf135da293d16fcc4cc607316742bd0ebb; From ca15a078bd907df5fc1c009477869c5cbde3b753 · fixed in 3d5127d998de617b130aae96b138dba22ac6a8a7; From ca15a078bd907df5fc1c009477869c5cbde3b753 · fixed in e41953e7d118e2702bcb217879c173d9d1d3cd4e; From ca15a078bd907df5fc1c009477869c5cbde3b753 · fixed in a2edbb6393972a02114b6003953a5cef3104fada; From ca15a078bd907df5fc1c009477869c5cbde3b753 · fixed in 1ceeebd5bd6d855b17a5df625109bfe29129d7cf; From ca15a078bd907df5fc1c009477869c5cbde3b753 · fixed in 86ab3e55673a7a49a841838776f1ab18d23a67b5

  • Linux Linux

    3.13

  • KernelLinux

    From 3.13.0 · 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