CVE-2025-39698: io_uring/futex: ensure io_futex_wait() cleans up properly on failure

Vulnerability summary

CVE-2025-39698 is a high (CVSS 7.8) Use After Free vulnerability in linux. EPSS estimates a 0.19% chance of exploitation in the next 30 days, higher than 9.1% of scored vulnerabilities.

Timeline

1. 05-09-2025
   PublishedVulnerability first disclosed.
2. 05-08-2026
   Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: io_uring/futex: ensure io_futex_wait() cleans up properly on failure The io_futex_data is allocated upfront and assigned to the io_kiocb async_data field, but the request isn't marked with REQ_F_ASYNC_DATA at that point. Those two should always go together, as the flag tells io_uring whether the field is valid or not. Additionally, on failure cleanup, the futex handler frees the data but does not clear ->async_data. Clear the data and the flag in the error path as well. Thanks to Trend Micro Zero Day Initiative and particularly ReDress for reporting this.

• 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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
• CWE-672Operation on a Resource after Expiration or ReleaseThe product uses, accesses, or otherwise operates on a resource after that resource has been expired, released, or revoked.