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

CVE-2026-43038
CRITICAL 9.8

At a glance

Source
NVD
EPSS
EPSS 0.26 % · percentile 17 ()
State
PUBLISHED
Published
Updated
Assigner
Linux
NVD status
Modified

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Description

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.

Weaknesses (CWE)

  • CWE-843 — Access of Resource Using Incompatible Type
  • CWE-787 — Out-of-bounds Write

References

Scores

VersionScoreVectorScored by
CVSS 3.1CRITICAL 9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HLinux
CVSS 3.1HIGH 7.3CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:Hredhat-SADP
CVSS 3.1CRITICAL 9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HNVD · 416baaa9-dc9f-4396-8d5f-8c081fb06d67 (Secondary)
CVSS 3.1HIGH 7.3CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:HNVD · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c (Secondary)

European references

CERT-FR advisories

Affected configurations (NVD CPE)

Affected products

ProductVersions
Linux · Linuxaffected ca15a078bd907df5fc1c009477869c5cbde3b753 < c438ba010171b70bad22fc18b1d5bdc3627476e8 ; affected ca15a078bd907df5fc1c009477869c5cbde3b753 < 0452b6526b2f54b2413b9cb4ff1ea2ac542c99c7 ; affected ca15a078bd907df5fc1c009477869c5cbde3b753 < a4437faf135da293d16fcc4cc607316742bd0ebb ; affected ca15a078bd907df5fc1c009477869c5cbde3b753 < 3d5127d998de617b130aae96b138dba22ac6a8a7 ; affected ca15a078bd907df5fc1c009477869c5cbde3b753 < e41953e7d118e2702bcb217879c173d9d1d3cd4e ; affected ca15a078bd907df5fc1c009477869c5cbde3b753 < a2edbb6393972a02114b6003953a5cef3104fada
Linux · Linuxaffected 3.13 ; unaffected 0 < 3.13 ; unaffected 5.10.253 ≤ 5.10.* ; unaffected 5.15.203 ≤ 5.15.* ; unaffected 6.1.168 ≤ 6.1.* ; unaffected 6.6.134 ≤ 6.6.*

Sources

SourceLicence
CVE List (CVEProject cvelistV5)CVE Program Terms of Use
EPSS (FIRST.org)FIRST — attribution requested
ENISA EUVDENISA — reproduction authorised, source acknowledged
CERT-FR (ANSSI)Licence Ouverte / Etalab 2.0
NVD (NIST) via fkie-cad/nvd-json-data-feedsPublic domain — this product uses data from the NVD API but is not endorsed or certified by the NVD