CVE-2026-23287 irqchip/sifive-plic: Fix frozen interrupt due to affinity setting

Medium 5.5 Published 25 Mar 2026 Updated 15 Oct 2026

A flaw in the Linux kernel's SiFive PLIC driver allows attackers to freeze UART interrupts by changing affinity settings, causing a 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-2026-23287?

CVE-2026-23287 is a medium-severity denial of service vulnerability in Linux kernel, published on 25 Mar 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:

irqchip/sifive-plic: Fix frozen interrupt due to affinity setting

PLIC ignores interrupt completion message for disabled interrupt, explained by the specification:

The PLIC signals it has completed executing an interrupt handler by writing the interrupt ID it received from the claim to the claim/complete register. The PLIC does not check whether the completion ID is the same as the last claim ID for that target. If the completion ID does not match an interrupt source that is currently enabled for the target, the completion is silently ignored.

This caused problems in the past, because an interrupt can be disabled while still being handled and plic_irq_eoi() had no effect. That was fixed by checking if the interrupt is disabled, and if so enable it, before sending the completion message. That check is done with irqd_irq_disabled().

However, that is not sufficient because the enable bit for the handling hart can be zero despite irqd_irq_disabled(d) being false. This can happen when affinity setting is changed while a hart is still handling the interrupt.

This problem is easily reproducible by dumping a large file to uart (which generates lots of interrupts) and at the same time keep changing the uart interrupt's affinity setting. The uart port becomes frozen almost instantaneously.

Fix this by checking PLIC's enable bit instead of irqd_irq_disabled().

Which versions are affected by CVE-2026-23287?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-23287?

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-2026-23287 being exploited?

There is no known exploitation of CVE-2026-23287 in the wild and no public exploit code.

All Linux kernel vulnerabilities

Sources

Also known as BELL-CVE-2026-23287, DEBIAN-CVE-2026-23287, GHSA-73mm-44q3-cmm6, ROOT-OS-DEBIAN-11-CVE-2026-23287, ROOT-OS-DEBIAN-12-CVE-2026-23287, ROOT-OS-DEBIAN-13-CVE-2026-23287 and 3 more.