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

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-09-05 · updated 2026-10-19
Weakness: CWE-416

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.

Affected products

Linux kernel: from 6.7 before 6.12.44; from 6.13 before 6.16.4; 6.17-rc1, 6.17-rc2 — fixed in 6.12.44, 6.16.4

How to fix

Upgrade to a fixed version: Linux kernel 6.12.44, 6.16.4. Check the vendor advisory for mitigations.

References

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