CVE-2021-3444 Linux kernel bpf verifier incorrect mod32 truncation
A local attacker can exploit a BPF verifier flaw to read kernel memory or execute code via out-of-bounds access.
- 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-2021-3444?
CVE-2021-3444 is a high-severity memory corruption vulnerability in Canonical Ubuntu Linux, published on 23 Mar 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
The bpf verifier in the Linux kernel did not properly handle mod32 destination register truncation when the source register was known to be 0. A local attacker with the ability to load bpf programs could use this gain out-of-bounds reads in kernel memory leading to information disclosure (kernel memory), and possibly out-of-bounds writes that could potentially lead to code execution. This issue was addressed in the upstream kernel in commit 9b00f1b78809 ("bpf: Fix truncation handling for mod32 dst reg wrt zero") and in Linux stable kernels 5.11.2, 5.10.19, and 5.4.101.
Which versions are affected by CVE-2021-3444?
It affects 3 products.
Products include Canonical Ubuntu Linux, Debian Debian Linux, Linux kernel.
How do I fix CVE-2021-3444?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2021-3444 being exploited?
There is no known exploitation of CVE-2021-3444 in the wild and no public exploit code.
Other vulnerabilities in Canonical Ubuntu Linux
Sources
Also known as A-183694099, DEBIAN-CVE-2021-3444, GHSA-c55x-85rg-x529, PUB-A-183694099, UBUNTU-CVE-2021-3444.