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Critical 9.8Published May 1, 2026

CVE-2026-43038ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach()

Updated under an hour ago ()

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It affects Linux and 11 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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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.

CVSS
9.8 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE)
CWE-843, CWE-787
Known exploited
Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days)
Not loaded for this CVE
Assigned by
Linux
NVD analysis
Modified
Record last updated
Oct 19, 2026
First seen by InfoSec Signals
Oct 9, 2026

Affected products

Affected products
Linux Linux
linux:linux (from the name)
from ca15a078bd907df5fc1c009477869c5cbde3b753 before c438ba010171b70bad22fc18b1d5bdc3627476e8; from ca15a078bd907df5fc1c009477869c5cbde3b753 before 0452b6526b2f54b2413b9cb4ff1ea2ac542c99c7; from ca15a078bd907df5fc1c009477869c5cbde3b753 before a4437faf135da293d16fcc4cc607316742bd0ebb; from ca15a078bd907df5fc1c009477869c5cbde3b753 before 3d5127d998de617b130aae96b138dba22ac6a8a7; from ca15a078bd907df5fc1c009477869c5cbde3b753 before e41953e7d118e2702bcb217879c173d9d1d3cd4e; from ca15a078bd907df5fc1c009477869c5cbde3b753 before a2edbb6393972a02114b6003953a5cef3104fada; from ca15a078bd907df5fc1c009477869c5cbde3b753 before 1ceeebd5bd6d855b17a5df625109bfe29129d7cf; from ca15a078bd907df5fc1c009477869c5cbde3b753 before 86ab3e55673a7a49a841838776f1ab18d23a67b5
CNA record
from 0:6.12.0-211.28.1.el10_2 not affected
CISA ADP
from 0:6.12.0-55.77.1.el10_0 not affected
CISA ADP
from 0:4.18.0-305.194.1.el8_4 not affected
CISA ADP
from 0:4.18.0-305.194.1.el8_4 not affected
CISA ADP
from 0:4.18.0-477.145.1.el8_8 not affected
CISA ADP
from 0:4.18.0-477.145.1.el8_8 not affected
CISA ADP
from 0:5.14.0-570.119.1.el9_6 not affected
CISA ADP
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name)
from V3.1.6
CISA ADP
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name)
from V3.1.6
CISA ADP

References

References

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.

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