CVE-2025-40176
A critical flaw in the Linux kernel’s TLS handling could let an attacker cause a use‑after‑free or overwrite user memory if an async decryption fails. The kernel now waits for all pending decryption requests when the allocation for a clone fails, preventing the vulnerability. The issue is fixed in recent kernel releases.
An official fix is available, so this entry is kept for 30 days and then removed automatically.
Who is affected
Linux kernel, all distributions that use affected kernel versions. Typical users are system administrators and end users of those distributions.
Real-world impact
An attacker could exploit the flaw to crash the system, cause a denial of service, or potentially execute arbitrary code by triggering a use‑after‑free or memory overwrite during TLS processing.
Why this severity
The CVSS score of 9.8 reflects the vulnerability’s high impact on confidentiality, integrity, and availability, and the fact that it can be exploited remotely without authentication or user interaction.
What to do about it
- 01Upgrade your Linux kernel to a version that includes the fix for CVE-2025-40176.
- 02Reboot the system to load the new kernel.
NVD description indicates the issue has been resolved in the Linux kernel.
Timeline
- Nov 12, 2025 · Nov 12, 2025PublishedDisclosed and added to the National Vulnerability Database.
- Jul 30, 2026 · 6d agoAdvisory updatedThe NVD record was last revised.
- Jul 30, 2026 · 6d agoOfficial fix availableA vendor patch or mitigation now exists — see the remediation steps above.