CVE-2026-52933 io_uring/poll: fix signed comparison in io_poll_get_ownership()
A signed comparison bug in the Linux kernel io_uring subsystem prevents the slowpath from executing when a cancel flag is set, potentially leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-52933?
CVE-2026-52933 is a high-severity vulnerability in Linux kernel, published on 24 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
io_uring/poll: fix signed comparison in io_poll_get_ownership()
io_poll_get_ownership() uses a signed comparison to check whether poll_refs has reached the threshold for the slowpath:
if (unlikely(atomic_read(&req->poll_refs) >= IO_POLL_REF_BIAS))
atomic_read() returns int (signed). When IO_POLL_CANCEL_FLAG (BIT(31)) is set in poll_refs, the value becomes negative in signed arithmetic, so the >= 128 comparison always evaluates to false and the slowpath is never taken.
Fix this by casting the atomic_read() result to unsigned int before the comparison, so that the cancel flag is treated as a large positive value and correctly triggers the slowpath.
Which versions are affected by CVE-2026-52933?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-52933?
Apply the vendor's patch.
Is CVE-2026-52933 being exploited?
There is no known exploitation of CVE-2026-52933 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-52933, DEBIAN-CVE-2026-52933, GHSA-37vf-c5qj-3jr7, ROOT-OS-DEBIAN-12-CVE-2026-52933, ROOT-OS-UBUNTU-2204-CVE-2026-52933, ROOT-OS-UBUNTU-2404-CVE-2026-52933 and 1 more.