CVE-2026-45927 bpf: Require frozen map for calculating map hash

Medium 4.7 Published 27 May 2026 Updated 27 May 2026

A time-of-check time-of-use race condition in the Linux kernel BPF subsystem allows attackers to bypass integrity checks by modifying map contents after hash calculation.

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-2026-45927?

CVE-2026-45927 is a medium-severity vulnerability in Linux kernel, published on 27 May 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:

bpf: Require frozen map for calculating map hash

Currently, bpf_map_get_info_by_fd calculates and caches the hash of the map regardless of the map's frozen state.

This leads to a TOCTOU bug where userspace can call BPF_OBJ_GET_INFO_BY_FD to cache the hash and then modify the map contents before freezing.

Therefore, a trusted loader can be tricked into verifying the stale hash while loading the modified contents.

Fix this by returning -EPERM if the map is not frozen when the hash is requested. This ensures the hash is only generated for the final, immutable state of the map.

Weakness: CWE-367

Which versions are affected by CVE-2026-45927?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-45927?

Apply the vendor's patch.

Is CVE-2026-45927 being exploited?

There is no known exploitation of CVE-2026-45927 in the wild and no public exploit code.

All Linux kernel vulnerabilities

Sources

Also known as BELL-CVE-2026-45927, DEBIAN-CVE-2026-45927, GHSA-mx29-fw97-m6gr, UBUNTU-CVE-2026-45927.