CVE-2026-53321 io_uring/napi: cap busy_poll_to 10 msec

What is CVE-2026-53321?

CVE-2026-53321 is a medium-severity denial of service vulnerability in Linux kernel, published on 26 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/napi: cap busy_poll_to 10 msec

Currently there's no cap on the maximum amount of time that napi is allowed to poll if no events are found, which can lead to kernel complaints on a task being stuck as there's no conditional rescheduling done within that loop.

Just cap it to 10 msec in total, that's already way above any kind of sane value that will reap any benefits, yet low enough that it's nowhere near being able to trigger preemption complaints.

Which versions are affected by CVE-2026-53321?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-53321?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-53321 being exploited?

There is no known exploitation of CVE-2026-53321 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2026-53321, DEBIAN-CVE-2026-53321, GHSA-g22f-3wv9-pgvj, ROOT-OS-DEBIAN-13-CVE-2026-53321, UBUNTU-CVE-2026-53321.