VulnerabilityPublished 6 May 2026Updated 6 Nov 2026

CVE-2026-43109: Linux kernel · x86: shadow stacks: proper error handling for mmap lock

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in c79cf42321600e931933e11f94aba8b245d4cd66 : update Linux kernel when convenient.

Data as of 6 Nov 2026, 16:18 UTC

Severity

Unrated

Rated by Threat Radar · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-06.

Patch

Available – fixed in c79cf42321600e931933e11f94aba8b245d4cd66, c64cebcc5c4f223dbcbe7dcdf74908fc092a0aa4, 262b6d38a81d51b135db81e1f30c13d30e38feee +2

Exploitation evidence

Disclosed: evidence found.
CVE published 6 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 6 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 7fad2a432cd35bbf104d2d9d426e74902f22aa95, < c79cf42321600e931933e11f94aba8b245d4cd66	Fixed in c79cf42321600e931933e11f94aba8b245d4cd66
LinuxLinux	Affected ≥ 7fad2a432cd35bbf104d2d9d426e74902f22aa95, < c64cebcc5c4f223dbcbe7dcdf74908fc092a0aa4	Fixed in c64cebcc5c4f223dbcbe7dcdf74908fc092a0aa4
LinuxLinux	Affected ≥ 7fad2a432cd35bbf104d2d9d426e74902f22aa95, < 262b6d38a81d51b135db81e1f30c13d30e38feee	Fixed in 262b6d38a81d51b135db81e1f30c13d30e38feee
LinuxLinux	Affected ≥ 7fad2a432cd35bbf104d2d9d426e74902f22aa95, < 52f657e34d7b21b47434d9d8b26fa7f6778b63a0	Fixed in 52f657e34d7b21b47434d9d8b26fa7f6778b63a0
LinuxLinux	Affected ≥ 7fad2a432cd35bbf104d2d9d426e74902f22aa95, < 1a30468eff661937d978495644d2e5ebfeef5ce6	Fixed in 1a30468eff661937d978495644d2e5ebfeef5ce6
LinuxLinux	Affected =6.6	Fixed in–

AI-suggested

A fix for this vulnerability is available in Linux kernel version 6.6 and related commits. Users and administrators should update to the fixed kernel version to remediate the issue.

Description

A vulnerability in the Linux kernel x86 shadow stacks implementation was fixed by improving error handling for mmap lock operations. Specifically, the function shstk_pop_sigframe() did not check for errors returned by mmap_read_lock_killable(), which could lead to improper handling of mmap locks. The issue was addressed by adding proper error checks and marking the relevant functions with __must_check to prevent similar oversights.

Impact

The vulnerability involves improper error handling in kernel memory management related to shadow stacks on x86 architectures. While the exact impact is not detailed, improper error handling in kernel locking mechanisms can potentially lead to stability issues or unexpected behavior. There is no indication of known exploitation in the wild.

Summary

CVE-2026-43109 addresses a flaw in the Linux kernel's x86 shadow stacks feature where the function shstk_pop_sigframe() failed to verify the return value of mmap_read_lock_killable(), an error in handling mmap locks. This oversight was corrected by implementing proper error checking and annotating the functions with __must_check to enforce error handling. The fix is included in the Linux kernel version 6.6 and associated commits.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 6 Nov 2026, 16:18 UTC

Technical details

References

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