CVE-2026-93834: Qemu-kvm: 9pfs: use-after-free race in tlcreate/twalk allows vm guest escape

Vulnerability summary

CVE-2026-93834 is a high (CVSS 8.8) Use After Free vulnerability in qemu. EPSS estimates a 0.40% chance of exploitation in the next 30 days, higher than 34.7% of scored vulnerabilities.

Timeline

1. 25-09-2026
   PublishedVulnerability first disclosed.
2. 31-10-2026
   Last modifiedVulnerability information updated.

Description

A use-after-free vulnerability was found in QEMU's 9pfs subsystem. A race condition between the main thread and a worker thread when processing concurrent Tlcreate and Twalk requests allows a malicious guest user to craft a fid path containing stale heap data, bypassing directory traversal restrictions and escaping the shared directory boundary. This can lead to arbitrary host file read/write and code execution (VM escape) as the QEMU process user.

• CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.