CVE-2026-43121: Linux kernel · io_uring/zcrx: fix user_ref race between scrub and refill paths
Affects Linux kernelSource GCVE Database
Not known to be exploited.
Data as of 11 Nov 2026, 22:48 UTC
Rated High by Threat Radar's AI analysis · No CVSS score from NVD or the CNA
Thin evidence
One scorer or noneExploitation evidence
Disclosed: evidence found.
CVE published 6 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 11 Nov 2026.
What to do
AI-suggested
A fix has been implemented that replaces the non-atomic decrement with an atomic compare-and-exchange loop in io_zcrx_put_niov_uref(), ensuring safe concurrent manipulation of user_refs. Users should apply the official Linux kernel patch that addresses this race condition. No additional mitigation steps are indicated.
Description
A race condition in the Linux kernel's io_uring subsystem involving user reference counting can lead to a double-free vulnerability. This occurs due to non-atomic operations on user_refs between the scrub and refill paths, causing out-of-bounds writes in kernel memory.