What Is CVE-2025-38352 (Linux POSIX CPU Timers Race Condition)?

By NHI Mgmt Group Updated October 20, 2026 Domain: Threats, Abuse & Incident Response

CVE-2025-38352 is a time-of-check time-of-use (TOCTOU) race condition vulnerability in Linux Kernel. CISA added it to the Known Exploited Vulnerabilities catalogue on 4 September 2025, which means attackers have used it in real attacks. Linux kernel contains a time-of-check time-of-use (TOCTOU) race condition vulnerability that has a high impact on confidentiality, integrity, and availability.

What This Vulnerability Means in Linux Kernel

CVE-2025-38352 is a time-of-check time-of-use race in the Linux kernel, which means the kernel can validate a condition and then act on it after the state has changed. That gap matters because kernel code runs with deep trust and small timing windows can become security boundaries.

TOCTOU flaws are dangerous in low-level operating system code because they can break assumptions about file state, process state, permissions, memory state, or other kernel-managed resources. In practice, a successful race can let an attacker bypass an intended check, trigger unsafe behaviour, or corrupt the control flow that the kernel was relying on to stay consistent.

Why Race Conditions Become Security Problems

Race conditions are especially serious when they sit inside the kernel’s scheduling, timer, or resource-handling paths. An attacker does not need to defeat the check itself, only to change the underlying condition before the use step runs, which turns an apparently safe decision into an exploitable inconsistency.

That is why time-of-check time-of-use issues often show up as privilege, integrity, or availability problems rather than simple crashes. The bug can create a path where the kernel makes a decision based on stale information and then applies that decision to a different state than the one it verified.

The Linux kernel is a high-value target for this class of flaw because exploitation can affect the whole system, not just one application. When a kernel race is real-world exploited, defenders should treat it as a priority exposure even before every technical detail of the exploit is understood.

How Organisations Should Check Exposure

The first step is to determine whether any Linux systems in scope run the affected kernel line and whether those systems are exposed to the condition in practice. Asset inventory, kernel version tracking, and vendor advisories are the fastest way to separate theoretical exposure from systems that need urgent attention.

Because this CVE was added to the CISA Known Exploited Vulnerabilities catalogue on 4 September 2025, organisations should assume that exposed systems may already be on an attacker’s shortlist and validate their fleet accordingly. The CVE Program is the authoritative record for the identifier, while the vendor advisory should be used for exact fix guidance.

For prioritisation, pair asset ownership with internet exposure, critical workload placement, and whether the system supports privileged administration, authentication, or sensitive services. The National Vulnerability Database is useful for central CVE reference and related metadata, but it should complement, not replace, local asset and configuration data.

Remediation, Detection, and Recovery

The preferred response is to apply the vendor’s fix as soon as operationally possible, because race-condition bugs are hard to neutralise reliably without correcting the underlying code. Where a patch cannot be deployed immediately, reduce exposure by limiting access to the affected systems, shrinking attack surface, and using compensating controls that reduce the chance of reaching the vulnerable path.

Detection should focus on suspicious kernel behaviour, unexplained failures, and signs of attempted exploitation around the affected timer or process path. After patching, review for compromise rather than assuming the system is clean, because exploitation of a kernel flaw can leave few obvious application-level traces.

For operational response, a vulnerable kernel should be treated like a trust-anchor problem, not just a software defect. Zero-Day and Exploited Vulnerabilities Guide and Vulnerability Management Guide both support the practical steps of triage, emergency mitigation, and verification after remediation.

Identity and System Impact After Exploitation

If an attacker uses a kernel exploit to gain stronger execution rights, the downstream concern is no longer only the bug itself. The important question becomes what the attacker could access, modify, or persist through after privilege is expanded.

That can include privileged sessions, service credentials, API keys, SSH material, or other secrets resident on the host, along with any management plane access that the system can reach. If exploitation is suspected, rotate the identities and secrets that were reachable from the compromised system and review whether those materials were exposed before the patch was applied.

When the vulnerable host supports administrative tooling, build systems, or other trust-heavy services, a kernel compromise can become a launch point for broader lateral movement. The post-patch review should therefore cover not only system integrity, but also whether any credentials, sessions, or keys need to be assumed compromised.

Risk and Threat Considerations

Kernel TOCTOU bugs are attractive to attackers because they can turn a narrow timing window into a high-impact bypass of a trusted decision. Once the race is reliably triggered, the attacker may be able to alter permissions, destabilise the system, or move from an ordinary user context into a much more privileged one.

Failure mechanism: the kernel checks a condition, then uses it after the state has changed, so the decision is applied to stale or attacker-influenced data.

Impact: exploitation can compromise confidentiality, integrity, or availability at the system level, and may also expose privileged credentials or enable follow-on compromise after the initial race is won.

Standards & Framework Alignment

This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.

MITRE ATT&CK addresses the attack and risk surface, while NIST SP 800-53 Rev 5, CIS Controls v8, NIST CSF 2.0 and NIST SP 800-57 set the governance and control requirements practitioners need to meet.

Framework	Control / Reference	Relevance
NIST SP 800-53 Rev 5	SI-2 — Flaw Remediation	Kernel CVEs require tracked remediation and verification of installed fixes.
	RA-5 — Vulnerability Monitoring and Scanning	Exposure to a known kernel CVE depends on inventory and scan coverage.
	CA-7 — Continuous Monitoring	Active exploitation makes ongoing monitoring and post-patch validation material to this CVE.
Recommendation — Prioritise SI-2 remediation for exposed Linux kernels and verify the vulnerable condition is eliminated. Use RA-5 to identify affected Linux assets and confirm where the vulnerable kernel is deployed. Extend CA-7 monitoring to detect exploitation indicators and validate patched hosts remain stable.
CIS Controls v8	CIS-7 — Continuous Vulnerability Management	This CVE requires asset-aware prioritisation, remediation, and verification across Linux endpoints.
	CIS-4 — Secure Configuration of Enterprise Assets and Software	Compensating controls and hardening reduce exposure when a vulnerable kernel cannot be patched immediately.
Recommendation — Apply CIS-7 to prioritise, remediate, and recheck exposed Linux kernel instances. Use CIS-4 to reduce attack surface on Linux systems until the kernel fix is deployed.
NIST CSF 2.0	ID.RA-01 — Asset Vulnerabilities Are Identified and Recorded	Known exploited CVEs require exposure discovery across the asset inventory.
	PR.DS-07 — Integrity Monitoring	Post-exploitation review for a kernel race depends on checking whether system integrity was altered.
Recommendation — Record exposed Linux kernels under ID.RA-01 and track them to remediation. Use PR.DS-07 to verify kernel-integrity indicators after patching and recovery.
MITRE ATT&CK	T1068 — Exploitation for Privilege Escalation	A kernel TOCTOU race can be used to obtain higher privileges on Linux systems.
	T1211 — Exploitation for Defense Evasion	Kernel exploitation can undermine host visibility and help adversaries stay hidden.
Recommendation — Map suspicious activity to T1068 and hunt for privilege-escalation paths through the kernel flaw. Investigate T1211-style exploitation when the kernel flaw is used to avoid or disable detection.
NIST SP 800-57	5.3 — Key Management Procedures	If exploitation reaches sensitive host material, key rotation and replacement become part of recovery.
Recommendation — Rotate exposed keys and credentials under 5.3 when kernel compromise may have disclosed them.

Practitioner Guidance

Why practitioners should care: A kernel race condition is not just a defect to schedule into normal maintenance. Because the vulnerability is already known to be exploited in the wild, exposure management should treat affected Linux hosts as urgent and verify whether they sit on critical paths, not merely whether they are patched eventually.

What to watch for: Focus on systems that are externally reachable, host privileged services, or have a history of delayed kernel maintenance. Those are the places where a small timing flaw is most likely to become an operational incident.

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NHIMG Editorial Note
Reviewed and updated by the NHIMG editorial team on October 20, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org

CVE-2025-38352 (Linux POSIX CPU Timers Race Condition)