CVE-2026-43038

/// Technical 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

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References