CVE-2026-63993
A critical flaw in the Linux kernel’s VXLAN implementation can cause a use‑after‑free by reusing a cached IP header after a PMTU check. This memory corruption could let an attacker take control of the system. The issue has been fixed in the kernel.
An official fix is available, so this entry is kept for 30 days and then removed automatically.
Who is affected
Linux kernel users running versions that contain the vulnerable VXLAN code.
Real-world impact
An attacker could exploit the use‑after‑free to corrupt memory and potentially execute arbitrary code on the affected system.
Why this severity
The CVSS score of 9.8 reflects that the vulnerability is network‑exploitable with no authentication or user interaction, and it can compromise confidentiality, integrity, and availability.
What to do about it
- 01Upgrade your Linux kernel to a version that includes the fix for the VXLAN use‑after‑free issue.
- 02Reboot the system to load the updated kernel.
NVD-referenced vendor advisory
Timeline
- Jul 19, 2026 · 14d agoPublishedDisclosed and added to the National Vulnerability Database.
- Jul 20, 2026 · 13d agoOfficial fix availableA vendor patch or mitigation now exists — see the remediation steps above.
- Jul 30, 2026 · 3d agoAdvisory updatedThe NVD record was last revised.
How it’s attacked
References & advisories
- git.kernel.org/stable/c/5303925e360527243b…
- git.kernel.org/stable/c/609e63312c29aad180…
- git.kernel.org/stable/c/6b8bfce9d2f774d2c2…
- git.kernel.org/stable/c/7d9ef0cb271555d8cf…
- git.kernel.org/stable/c/8d435d68d71fb87587…
- git.kernel.org/stable/c/9257f56ac47ef1976b…
- git.kernel.org/stable/c/a493efd4336cf19122…
- git.kernel.org/stable/c/dc3bfa050f873371e7…