CVE-2025-38352: Linux Kernel Time-of-Check Time-of-Use (TOCTOU) Race Condition Vulnerability

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Yes, if you run Linux Kernel. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2025-09-04, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2025-09-25; treat that as the outer limit, not the target.
• EPSS 1.3%, percentile 71: FIRST’s model estimates a 1.3% chance of exploitation activity in the next 30 days, higher than 71% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Needs local access needed. Lower urgency for most teams unless an attacker could already run code on the machine.

What it is

In the Linux kernel, the following vulnerability has been resolved: posix-cpu-timers: fix race between handleposixcputimers() and posixcputimerdel() If an exiting non-autoreaping task has already passed exitnotify() and calls handleposixcputimers() from IRQ, it can be reaped by its parent or debugger right after unlocktasksighand(). If a concurrent posixcputimerdel() runs at that moment, it won't be able to detect timer->it.cpu.firing != 0: cputimertaskrcu() and/or locktasksighand() will fail. Add the tsk->exitstate check into runposixcputimers() to fix this. This fix is not needed if CONFIGPOSIXCPUTIMERSTASKWORK=y, because exittaskwork() is called before exitnotify(). But the check still makes sense, taskworkadd(&tsk->posixcputimerswork.work) will fail anyway in this case.

CISA’s summary

Linux kernel contains a time-of-check time-of-use (TOCTOU) race condition vulnerability that has a high impact on confidentiality, integrity, and availability.

Weakness type: CWE-367.

Product: Linux Kernel · Assigned by: Linux · Published: 2025-07-22

Affected and fixed versions

Severity scores

• Attack vector: local access needed
• Attack complexity: low
• Privileges required: low (any account)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: added 2025-09-04; federal due date 2025-09-25. Known ransomware use: Unknown.
• CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
• CISA SSVC assessment: exploitation active, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 1.34% probability of exploitation activity in the next 30 days; percentile 71.

Timeline

• 2025-07-22 — CVE record published by Linux
• 2025-09-04 — Added to CISA’s Known Exploited Vulnerabilities catalog
• 2025-09-25 — CISA remediation deadline for US federal agencies
• 2026-09-08 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. Listed in CISA KEV notes (git.kernel.org) git.kernel.org
2. Listed in CISA KEV notes (source.android.com) source.android.com

Vulnerability records

1. CVE.org record CVE-2025-38352 cve.org
2. NVD entry CVE-2025-38352 nvd.nist.gov

Government

1. CISA Known Exploited Vulnerabilities catalog entry cisa.gov

Other references from the CVE record and advisory

1. git.kernel.org git.kernel.org
2. git.kernel.org git.kernel.org
3. git.kernel.org git.kernel.org
4. git.kernel.org git.kernel.org
5. git.kernel.org git.kernel.org
6. git.kernel.org git.kernel.org
7. git.kernel.org git.kernel.org
8. git.kernel.org git.kernel.org
9. github.com github.com
10. lists.debian.org lists.debian.org
11. lists.debian.org lists.debian.org

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