Use After Free in Linux
CVE-2025-21655
In the Linux kernel, the following vulnerability has been resolved: io_uring/eventfd: ensure io_eventfd_signal() defers another RCU period io_eventfd_do_signal() is invoked from an RCU callback, but when dropping the reference to the io_ev_fd, it calls io_eventfd_free() directly if the refcount drops to zero. This isn't correct, as any potential freeing of the io_ev_fd should be deferred another RCU grace period. Just call io_eventfd_put() rather than open-code the dec-and-test and free, which will correctly defer it another RCU grace period.
Vulnerability class: Use-After-Free
EPSS: 0.002 (12.6th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.8 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
Affected products
- Linux — versions 21a091b970cdbcf3e8ff829234b51be6f9192766, 6.1, 0
- Linux Linux_kernel — versions 6.13
Weakness classification (CWE)
Public proof-of-concept exploits
References
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67 (Patch)
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67 (Patch)
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67 (Patch)
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67 (Patch)
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67 (Third Party Advisory, Issue Tracking)
- af854a3a-2127-422b-91ae-364da2661108
- 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
Frequently asked questions
- What is CVE-2025-21655?
- CVE-2025-21655 is a high-severity vulnerability in Linux, classified under Use After Free. CVSS score: 7.8/10. Published 2025-01-20.
- How severe is CVE-2025-21655?
- High severity. CVSS v3 base score is 7.8 out of 10.
- Is CVE-2025-21655 known to be exploited?
- 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.