CVE-2026-43121
4.7 · MEDIUMOverview
CVE-2026-43121 is a medium-severity vulnerability affecting linux linux_kernel. It was published on May 6, 2026 and has a CVSS 3.1 base score of 4.7 (MEDIUM).
This vulnerability has a CVSS 3.1 base score of 4.7, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.
Technical Description
In the Linux kernel, the following vulnerability has been resolved:
io_uring/zcrx: fix user_ref race between scrub and refill paths
The io_zcrx_put_niov_uref() function uses a non-atomic
check-then-decrement pattern (atomic_read followed by separate
atomic_dec) to manipulate user_refs. This is serialized against other
callers by rq_lock, but io_zcrx_scrub() modifies the same counter with
atomic_xchg() WITHOUT holding rq_lock.
On SMP systems, the following race exists:
CPU0 (refill, holds rq_lock) CPU1 (scrub, no rq_lock)
put_niov_uref:
atomic_read(uref) - 1
// window opens
atomic_xchg(uref, 0) - 1
return_niov_freelist(niov) [PUSH #1]
// window closes
atomic_dec(uref) - wraps to -1
returns true
return_niov(niov)
return_niov_freelist(niov) [PUSH #2: DOUBLE-FREE]
The same niov is pushed to the freelist twice, causing free_count to
exceed nr_iovs. Subseque
Remediation
Check the references section for vendor advisories and patches from linux. Update linux_kernel to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| linux | linux_kernel | >= 6.15, < 6.18.16 | Affected |
Frequently Asked Questions
What is CVE-2026-43121?
CVE-2026-43121 is a medium-severity vulnerability affecting linux linux_kernel. It was published on May 6, 2026 and has a CVSS 3.1 base score of 4.7 (MEDIUM).
How severe is CVE-2026-43121?
This vulnerability has a CVSS 3.1 base score of 4.7, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.
How do I fix or remediate CVE-2026-43121?
Check the references section for vendor advisories and patches from linux. Update linux_kernel to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-43121?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-43121 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
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