CVE-2026-23177 mm, shmem: prevent infinite loop on truncate race

Q: Is CVE-2026-23177 being exploited?

There is no known exploitation of CVE-2026-23177 in the wild and no public exploit code.

Not scored Published 14 Feb 2026 Updated 11 May 2026

A race condition in the Linux kernel's shmem truncation logic can cause an infinite loop, leading to a local denial of service.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Local or same network only
Victim action needed: Not needed
Fix: Available

What is CVE-2026-23177?

CVE-2026-23177 is a denial of service vulnerability in Linux, published on 14 Feb 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:

mm, shmem: prevent infinite loop on truncate race

When truncating a large swap entry, shmem_free_swap() returns 0 when the entry's index doesn't match the given index due to lookup alignment. The failure fallback path checks if the entry crosses the end border and aborts when it happens, so truncate won't erase an unexpected entry or range. But one scenario was ignored.

When `index` points to the middle of a large swap entry, and the large swap entry doesn't go across the end border, find_get_entries() will return that large swap entry as the first item in the batch with `indices[0]` equal to `index`. The entry's base index will be smaller than `indices[0]`, so shmem_free_swap() will fail and return 0 due to the "base < index" check. The code will then call shmem_confirm_swap(), get the order, check if it crosses the END boundary (which it doesn't), and retry with the same index.

The next iteration will find the same entry again at the same index with same indices, leading to an infinite loop.

Fix this by retrying with a round-down index, and abort if the index is smaller than the truncate range.

Which versions are affected by CVE-2026-23177?

How do I fix CVE-2026-23177?

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-2026-23177 being exploited?