{"id":"CVE-2026-43038","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach()\n\nSashiko AI-review observed:\n\n  In ip6_err_gen_icmpv6_unreach(), the skb is an outer IPv4 ICMP error packet…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach()\n\nSashiko AI-review observed:\n\n  In ip6_err_gen_icmpv6_unreach(), the skb is an outer IPv4 ICMP error packet…","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cwe":["CWE-843"],"vendor":"linux","product":"linux_kernel","affected":["linux_kernel > 3.13, < 5.10.253","linux_kernel >= 5.11, < 5.15.203","linux_kernel >= 5.16, < 6.1.168","linux_kernel >= 6.2, < 6.6.134","linux_kernel >= 6.7, < 6.12.81","linux_kernel >= 6.13, < 6.18.22","linux_kernel >= 6.19, < 6.19.12","linux_kernel = 3.13","linux_kernel = 7.0"],"patched":["linux_kernel 6.19.12"],"published":"2026-05-01","updated":"2026-08-18","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-43038","references":[{"url":"https://git.kernel.org/stable/c/0452b6526b2f54b2413b9cb4ff1ea2ac542c99c7","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/1ceeebd5bd6d855b17a5df625109bfe29129d7cf","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/3d5127d998de617b130aae96b138dba22ac6a8a7","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/86ab3e55673a7a49a841838776f1ab18d23a67b5","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a2edbb6393972a02114b6003953a5cef3104fada","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a4437faf135da293d16fcc4cc607316742bd0ebb","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/c438ba010171b70bad22fc18b1d5bdc3627476e8","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/e41953e7d118e2702bcb217879c173d9d1d3cd4e","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://access.redhat.com/errata/RHSA-2026:22900","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:22940","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:22964","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:23224","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:23237","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:24343","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:25120","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:25121","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:25533","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:26535","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:30129","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:30848","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:55618","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:55762","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:55763","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:55837","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/security/cve/CVE-2026-43038","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2464397","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-082556.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43038.json","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"}],"tags":["nvd","cve.org"],"epss":0.00255,"epssPercentile":0.17445,"ingestedAt":"2026-08-18T13:17:08.782Z","slug":"CVE-2026-43038","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach()\n\nSashiko AI-review observed:\n\n  In ip6_err_gen_icmpv6_unreach(), the skb is an outer IPv4 ICMP error packet\n  where its cb contains an IPv4 inet_skb_parm. When skb is cloned into skb2\n  and passed to icmp6_send(), it uses IP6CB(skb2).\n\n  IP6CB interprets the IPv4 inet_skb_parm as an inet6_skb_parm. The cipso\n  offset in inet_skb_parm.opt directly overlaps with dsthao in inet6_skb_parm\n  at offset 18.\n\n  If an attacker sends a forged ICMPv4 error with a CIPSO IP option, dsthao\n  would be a non-zero offset. Inside icmp6_send(), mip6_addr_swap() is called\n  and uses ipv6_find_tlv(skb, opt->dsthao, IPV6_TLV_HAO).\n\n  This would scan the inner, attacker-controlled IPv6 packet starting at that\n  offset, potentially returning a fake TLV without checking if the remaining\n  packet length can hold the full 18-byte struct ipv6_destopt_hao.\n\n  Could mip6_addr_swap() then perform a 16-byte swap that extends past the end\n  of the packet data into skb_shared_info?\n\n  Should the cb array also be cleared in ip6_err_gen_icmpv6_unreach() and\n  ip6ip6_err() to prevent this?\n\nThis patch implements the first suggestion.\n\nI am not sure if ip6ip6_err() needs to be changed.\nA separate patch would be better anyway.\n\n## Affected\n\n- `linux_kernel > 3.13, < 5.10.253`\n- `linux_kernel >= 5.11, < 5.15.203`\n- `linux_kernel >= 5.16, < 6.1.168`\n- `linux_kernel >= 6.2, < 6.6.134`\n- `linux_kernel >= 6.7, < 6.12.81`\n- `linux_kernel >= 6.13, < 6.18.22`\n- `linux_kernel >= 6.19, < 6.19.12`\n- `linux_kernel = 3.13`\n- `linux_kernel = 7.0`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 6.19.12`","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}