--- id: CVE-2026-43038 title: |- 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… 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… 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: 0.00442 epssPercentile: 0.35773 ingestedAt: '2026-08-18T13:17:08.782Z' --- ## Overview 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. ## 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` ## Remediation Upgrade past the affected range: - `linux_kernel 6.19.12`