CVE-2026-43038 — ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach()
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.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.3% (30-day exploitation probability)+2
- Technical severity (critical)+10
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Linux Linux, Linux Linux Kernel).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- Apply the fixed version or the patch documented under Remediation.
- Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Linux | Linux |
version 3.13≥ ca15a078bd907df5fc1c009477869c5cbde3b753 and < 86ab3e55673a7a49a841838776f1ab18d23a67b5≥ ca15a078bd907df5fc1c009477869c5cbde3b753 and < 1ceeebd5bd6d855b17a5df625109bfe29129d7cf≥ ca15a078bd907df5fc1c009477869c5cbde3b753 and < a2edbb6393972a02114b6003953a5cef3104fada≥ ca15a078bd907df5fc1c009477869c5cbde3b753 and < e41953e7d118e2702bcb217879c173d9d1d3cd4e≥ ca15a078bd907df5fc1c009477869c5cbde3b753 and < 3d5127d998de617b130aae96b138dba22ac6a8a7≥ ca15a078bd907df5fc1c009477869c5cbde3b753 and < a4437faf135da293d16fcc4cc607316742bd0ebb≥ ca15a078bd907df5fc1c009477869c5cbde3b753 and < 0452b6526b2f54b2413b9cb4ff1ea2ac542c99c7 and 1 more≥ ca15a078bd907df5fc1c009477869c5cbde3b753 and < c438ba010171b70bad22fc18b1d5bdc3627476e8 |
Vulnerable | CVE Program (cve.org) e CISA ADP |
| Linux | Linux Kernel |
version 7.0-rc1version 7.0-rc6version 7.0-rc5version 7.0-rc4version 7.0-rc3version 7.0-rc2> 3.13 and < 5.10.253version 3.13-rc8 and 12 moreversion 3.13-rc7version 3.13-rc6version 3.13-rc5version 3.13-rc4version 3.13-rc3version 3.13≥ 6.19 and < 6.19.12≥ 6.13 and < 6.18.22≥ 6.7 and < 6.12.81≥ 6.2 and < 6.6.134≥ 5.16 and < 6.1.168≥ 5.11 and < 5.15.203 |
Vulnerable | NIST National Vulnerability Database |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 9.8 | CVSS 3.1 | Critical | 3.9 | 5.9 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 via NIST National Vulnerability Database |
| 9.8 | CVSS 3.1 | Critical | — | — | GitHub, Inc. via GitHub Security Advisories |
| 9.8 | CVSS 3.1 | Critical | — | — | Linux via CVE Program (cve.org) e CISA ADP |
| 7.3 | CVSS 3.1 | High | 1.8 | 5.5 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c via NIST National Vulnerability Database |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: 416baaa9-dc9f-4396-8d5f-8c081fb06d67) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
EPSS over time FIRST
Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.26%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
- Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · linux/linux
- Record published
- Fix documented
- CVSS changed · 9.8
- Source status changed · → Modified
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 2× References added · Oct 14, 2026 – Oct 14, 2026
- 1× Official description updated · Oct 13, 2026 – Oct 13, 2026
References
35 on the record
- git.kernel.org/stable/c/c438ba010171b70bad22fc18b1d5bdc3627476e8
- git.kernel.org/stable/c/3d5127d998de617b130aae96b138dba22ac6a8a7
- git.kernel.org/stable/c/86ab3e55673a7a49a841838776f1ab18d23a67b5
- git.kernel.org/stable/c/e41953e7d118e2702bcb217879c173d9d1d3cd4e
- git.kernel.org/stable/c/1ceeebd5bd6d855b17a5df625109bfe29129d7cf
- git.kernel.org/stable/c/a4437faf135da293d16fcc4cc607316742bd0ebb
- git.kernel.org/stable/c/0452b6526b2f54b2413b9cb4ff1ea2ac542c99c7
- git.kernel.org/stable/c/a2edbb6393972a02114b6003953a5cef3104fada
- access.redhat.com/errata/RHSA-2026:55618
- access.redhat.com/errata/RHSA-2026:22964
- access.redhat.com/security/cve/CVE-2026-43038
- cert-portal.siemens.com/productcert/html/ssa-019113.html
- access.redhat.com/errata/RHSA-2026:55762
- nvd.nist.gov/vuln/detail/CVE-2026-43038
- github.com/advisories/GHSA-78m7-4xgc-xrrq
- access.redhat.com/errata/RHSA-2026:30129
- access.redhat.com/errata/RHSA-2026:56224
- access.redhat.com/errata/RHSA-2026:55761
- access.redhat.com/errata/RHSA-2026:25121
- access.redhat.com/errata/RHSA-2026:30848
- bugzilla.redhat.com/show_bug.cgi
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43038.json
- cert-portal.siemens.com/productcert/html/ssa-457936.html
- access.redhat.com/errata/RHSA-2026:56225
- access.redhat.com/errata/RHSA-2026:55763
- access.redhat.com/errata/RHSA-2026:25120
- cert-portal.siemens.com/productcert/html/ssa-082556.html
- access.redhat.com/errata/RHSA-2026:25533
- access.redhat.com/errata/RHSA-2026:26535
- access.redhat.com/errata/RHSA-2026:23237
- access.redhat.com/errata/RHSA-2026:55837
- access.redhat.com/errata/RHSA-2026:22940
- access.redhat.com/errata/RHSA-2026:22900
- access.redhat.com/errata/RHSA-2026:23224
- access.redhat.com/errata/RHSA-2026:24343
Elsewhere on this site
Related CVEs (same products)
- Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 11h
- Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 11h
- Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
- Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 1d
- Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
- Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 1d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No CISA SSVC assessment.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-43038 is "ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach()", rated Critical. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.8 describes technical severity. EPSS 0.26% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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