VulnerabilityPublished 22 Aug 2026Updated 6 Nov 2026

CVE-2026-74636: Linux kernel · tracing: Fix race between update_event_fields and, event_define_fields

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in fdeb190b0905a6aaed1e5d6adfb8613214748d7d : update Linux kernel when convenient.

Data as of 6 Nov 2026, 17:55 UTC

Severity

Medium

Rated Medium by Threat Radar's AI analysis · CVSS not yet scored by NVD

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 fdeb190b0905a6aaed1e5d6adfb8613214748d7d, f128740f39ab28d1f4ad5bdd10f3e117eec0c374, ed49684e69f846bf50b5050651ccdb87cfd152c0 +7

Exploitation evidence

Disclosed: evidence found.
CVE published 22 Aug 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 >=5.15.33 <5.15.216 >=5.16.19 <5.17 >=5.17.2 <5.18	Fixed in fdeb190b0905a6aaed1e5d6adfb8613214748d7d f128740f39ab28d1f4ad5bdd10f3e117eec0c374 ed49684e69f846bf50b5050651ccdb87cfd152c0 e5f1d301b4bdaa4206db251fdc691f623162b0a8 c3730b8373bb5059d735509b9e6a00d7eb337d7c a30d421468300b1e7b2f233136aeb2db8013f555 5.18 5.17 5.15.216 4e39f7b4d9d36508c53e89e6cbc640728df870b5
LinuxLinux	Affected =5.18	Fixed in–

AI-suggested

A fix is available in Linux kernel versions 5.15.216, 5.17, 5.18, and corresponding commits. Users should upgrade to these fixed versions or later to mitigate the race condition. No additional mitigation is required once patched.

Description

A race condition vulnerability in the Linux kernel tracing subsystem was fixed. The race occurs between the functions update_event_fields and event_define_fields during module loading, leading to a kernel panic due to unprotected access to shared data structures. The issue is resolved by acquiring the event_mutex lock in trace_event_update_all before accessing shared fields.

Impact

The vulnerability can cause a kernel panic during concurrent module loading, resulting in denial of service due to system crash. There is no indication of privilege escalation or code execution. The impact is limited to system stability and availability.

Summary

CVE-2026-74636 addresses a race condition in the Linux kernel's tracing subsystem where concurrent loading of kernel modules can cause unsynchronized access to the class->fields list. Specifically, event_define_fields() adds fields to the list under event_mutex protection, but update_event_fields() accesses the same list without holding event_mutex, leading to a race and kernel panic. The fix involves taking event_mutex in trace_event_update_all() before acquiring trace_event_sem, ensuring proper synchronization and preventing the race condition.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 6 Nov 2026, 17:55 UTC

Technical details

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