CVE-2026-64259: fuse-uring: make a fuse_req on SQE commit only findable after memcpy

Vulnerability summary

CVE-2026-64259 is a high (CVSS 7.8) Use After Free vulnerability in linux. EPSS estimates a 0.17% chance of exploitation in the next 30 days, higher than 6.1% of scored vulnerabilities.

Timeline

1. 25-07-2026
   PublishedVulnerability first disclosed.
2. 17-08-2026
   Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: fuse-uring: make a fuse_req on SQE commit only findable after memcpy Bad userspace might try to trick us and send commit SQEs request unique / commit-id of requests that are not even send to fuse-server (io_uring_cmd_done() not called) yet. fuse_uring_commit_fetch() ends the fuse request when the ring entry has a wrong state, but that could have caused a use-after-free with the memcpy operations in fuse_uring_send_in_task(). In order to avoid such races the call of fuse_uring_add_to_pq() is moved after the copy operations and just before completing the io-uring request - malicious userspace cannot find the request anymore until all prepration work in fuse-client/kernel is completed. This also moves fuse_uring_add_to_pq() a bit up in the code to avoid a forward declaration. Also not with a preparation commit, to make it easier to back port to older kernels.

• 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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.