Kernel timer corruption via armed timer release
Published Aug 14, 2026 · Updated Aug 14, 2026
Use-after-free in Zephyr RTOS 1.12.0 through 4.4.2 allows local users to corrupt kernel timer state via an armed dynamic timer. The unref_check() path frees the timer without unlinking its _timeout node, so expiration consumes freed or reallocated kernel memory. Reachability requires CONFIG_USERSPACE, CONFIG_DYNAMIC_OBJECTS, and the timer's last permission; the PoC demonstrates callback confusion, not direct CPU privilege escalation.
Summary
What happened
Use-after-free in Zephyr RTOS 1.12.0 through 4.4.2 allows local users to corrupt kernel timer state via an armed dynamic timer. The unref_check() path frees the timer without unlinking its _timeout node, so expiration consumes freed or reallocated kernel memory. Reachability requires CONFIG_USERSPACE, CONFIG_DYNAMIC_OBJECTS, and the timer's last permission; the PoC demonstrates callback confusion, not direct CPU privilege escalation.
The record
- CVE
- CVE-2026-12366
- Published
- Aug 14, 2026
- Updated
- Aug 14, 2026
- Vendor
- Zephyr Project
- Product
- Zephyr RTOS
- Classifications
- CWE-416, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Aug 14, 2026CVE publishedPublication date reported by the CVE source.
- Aug 14, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=1.12.0 <4.5.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- Zephyr dynamic timer release and reuse PoCproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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