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

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Summary

CVECVE-2026-43038
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-01 15:16:48 UTC
Updated2026-05-03 07:16:23 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.000240000 probability, percentile 0.068220000 (date 2026-05-02)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected ca15a078bd907df5fc1c009477869c5cbde3b753 c438ba010171b70bad22fc18b1d5bdc3627476e8 git Not specified
CNA Linux Linux affected ca15a078bd907df5fc1c009477869c5cbde3b753 0452b6526b2f54b2413b9cb4ff1ea2ac542c99c7 git Not specified
CNA Linux Linux affected ca15a078bd907df5fc1c009477869c5cbde3b753 a4437faf135da293d16fcc4cc607316742bd0ebb git Not specified
CNA Linux Linux affected ca15a078bd907df5fc1c009477869c5cbde3b753 3d5127d998de617b130aae96b138dba22ac6a8a7 git Not specified
CNA Linux Linux affected ca15a078bd907df5fc1c009477869c5cbde3b753 e41953e7d118e2702bcb217879c173d9d1d3cd4e git Not specified
CNA Linux Linux affected ca15a078bd907df5fc1c009477869c5cbde3b753 a2edbb6393972a02114b6003953a5cef3104fada git Not specified
CNA Linux Linux affected ca15a078bd907df5fc1c009477869c5cbde3b753 1ceeebd5bd6d855b17a5df625109bfe29129d7cf git Not specified
CNA Linux Linux affected ca15a078bd907df5fc1c009477869c5cbde3b753 86ab3e55673a7a49a841838776f1ab18d23a67b5 git Not specified
CNA Linux Linux affected 3.13 Not specified
CNA Linux Linux unaffected 3.13 semver Not specified
CNA Linux Linux unaffected 5.10.253 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.203 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.168 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.134 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.81 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.22 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.12 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/3d5127d998de617b130aae96b138dba22ac6a8a7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a4437faf135da293d16fcc4cc607316742bd0ebb 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0452b6526b2f54b2413b9cb4ff1ea2ac542c99c7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a2edbb6393972a02114b6003953a5cef3104fada 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/86ab3e55673a7a49a841838776f1ab18d23a67b5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c438ba010171b70bad22fc18b1d5bdc3627476e8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/1ceeebd5bd6d855b17a5df625109bfe29129d7cf 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/e41953e7d118e2702bcb217879c173d9d1d3cd4e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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