CVE-2026-43038: Linux kernel · ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach()
Affects Linux kernelSource CVE Database V5
Not known to be exploited · CVSS 9.8 Critical · fixed in e41953e7d118e2702bcb217879c173d9d1d3cd4e : patch Linux kernel as a priority.
Data as of 26 Oct 2026, 14:18 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 16% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- CISA SSVC
- Exploitation
- No evidence of active exploitation and no public proof of concept
- Automatable
- Attackers can reliably automate steps 1–4 of the kill chain
- Technical impact
- Total control over the software or total information disclosure
CISA SSVC assessment, 2026-10-16.
- Patch
- Available – fixed in e41953e7d118e2702bcb217879c173d9d1d3cd4e, c438ba010171b70bad22fc18b1d5bdc3627476e8, a4437faf135da293d16fcc4cc607316742bd0ebb +5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 1 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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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.
References
- git.kernel.org/stable/c/c438ba010171b70bad22fc18b1d5bdc3627476e8 (opens in a new tab)
- git.kernel.org/stable/c/0452b6526b2f54b2413b9cb4ff1ea2ac542c99c7 (opens in a new tab)
- git.kernel.org/stable/c/a4437faf135da293d16fcc4cc607316742bd0ebb (opens in a new tab)
- git.kernel.org/stable/c/3d5127d998de617b130aae96b138dba22ac6a8a7 (opens in a new tab)
- git.kernel.org/stable/c/e41953e7d118e2702bcb217879c173d9d1d3cd4e (opens in a new tab)
- git.kernel.org/stable/c/a2edbb6393972a02114b6003953a5cef3104fada (opens in a new tab)
- git.kernel.org/stable/c/1ceeebd5bd6d855b17a5df625109bfe29129d7cf (opens in a new tab)
- git.kernel.org/stable/c/86ab3e55673a7a49a841838776f1ab18d23a67b5 (opens in a new tab)
- access.redhat.com/security/cve/CVE-2026-43038 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2464397 (opens in a new tab)
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43038.json (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:24343 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:30129 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:22940 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:23237 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:23224 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:30848 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:55618 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:25121 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:55762 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:26535 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:25533 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:22964 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:55761 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:55837 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:56224 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:56225 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:55763 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:25120 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:22900 (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-082556.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-019113.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-457936.html (opens in a new tab)