CVE-2026-43139
HIGHDescription
In the Linux kernel, the following vulnerability has been resolved: xfrm6: fix uninitialized saddr in xfrm6_get_saddr() xfrm6_get_saddr() does not check the return value of ipv6_dev_get_saddr(). When ipv6_dev_get_saddr() fails to find a suitable source address (returns -EADDRNOTAVAIL), saddr->in6 is left uninitialized, but xfrm6_get_saddr() still returns 0 (success). This causes the caller xfrm_tmpl_resolve_one() to use the uninitialized address in xfrm_state_find(), triggering KMSAN warning: ===================================================== BUG: KMSAN: uninit-value in xfrm_state_find+0x2424/0xa940 xfrm_state_find+0x2424/0xa940 xfrm_resolve_and_create_bundle+0x906/0x5a20 xfrm_lookup_with_ifid+0xcc0/0x3770 xfrm_lookup_route+0x63/0x2b0 ip_route_output_flow+0x1ce/0x270 udp_sendmsg+0x2ce1/0x3400 inet_sendmsg+0x1ef/0x2a0 __sock_sendmsg+0x278/0x3d0 __sys_sendto+0x593/0x720 __x64_sys_sendto+0x130/0x200 x64_sys_call+0x332b/0x3e70 do_syscall_64+0xd3/0xf80 entry_SYSCALL_64_after_hwframe+0x77/0x7f Local variable tmp.i.i created at: xfrm_resolve_and_create_bundle+0x3e3/0x5a20 xfrm_lookup_with_ifid+0xcc0/0x3770 ===================================================== Fix by checking the return value of ipv6_dev_get_saddr() and propagating the error.
How to fix
This vulnerability affects an unusually large number of packages. The highest-confidence fixes are shown above; the full list is longer. Check the referenced advisories for complete coverage.
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Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
Exploit Intelligence
Low risk: more likely to be exploited than 31% of all known CVEs.
References
Related Vulnerabilities
Other CWE-908 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2025-5777 | High | 7.5 | 100% | KEV + Ransom | Fix |
| CVE-2023-24941 | Critical | 9.8 | 95% | - | Fix |
| CVE-2007-1751 | High | 9.3 | 61% | - | - |
| CVE-2008-0081 | Critical | 9.8 | 58% | - | - |
| CVE-2020-1934 | Medium | 5.3 | 52% | - | Fix |
| CVE-2011-1255 | High | 9.3 | 42% | - | - |
Common questions
How do I fix CVE-2026-43139?
Published advisories record a fix for 252 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2026-43139 being actively exploited?
Not that we know of. CVE-2026-43139 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.38% is the estimated probability that it will be exploited in the next 30 days. That is higher than 31% of all scored CVEs.
How severe is CVE-2026-43139?
CVE-2026-43139 has a CVSS v3 base score of 8.6, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-43139 affect?
Published advisories record a fix for linux (Debian), linux (Ubuntu), linux-aws (Ubuntu), linux-aws-5.15 (Ubuntu), and 248 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-10-19.