CVE-2021-3347 Use after free in n/a

High 7.8 Published 29 Jan 2021 Updated 25 Feb 2026

Local attackers can exploit a use-after-free in PI futexes to execute arbitrary code in the kernel, leading to privilege escalation.

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-2021-3347?

CVE-2021-3347 is a high-severity use after free vulnerability in Debian Debian Linux, published on 29 Jan 2021. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

An issue was discovered in the Linux kernel through 5.10.11. PI futexes have a kernel stack use-after-free during fault handling, allowing local users to execute code in the kernel, aka CID-34b1a1ce1458.

Weakness: CWE-416

Which versions are affected by CVE-2021-3347?

It affects 3 products.

Linux distribution packages (18)

`kpatch-patch-3_10_0-1160` Red Hat:enterprise_linux:7::server	All versions	`0:1-6.el7`
`kpatch-patch-3_10_0-1160-debuginfo` Red Hat:enterprise_linux:7::server	All versions	`0:1-6.el7`
`kpatch-patch-3_10_0-1160_11_1` Red Hat:enterprise_linux:7::server	All versions	`0:1-5.el7`
`kpatch-patch-3_10_0-1160_11_1-debuginfo` Red Hat:enterprise_linux:7::server	All versions	`0:1-5.el7`
`kpatch-patch-3_10_0-1160_15_2` Red Hat:enterprise_linux:7::server	All versions	`0:1-5.el7`
`kpatch-patch-3_10_0-1160_15_2-debuginfo` Red Hat:enterprise_linux:7::server	All versions	`0:1-5.el7`
`kpatch-patch-3_10_0-1160_21_1` Red Hat:enterprise_linux:7::server	All versions	`0:1-3.el7`
`kpatch-patch-3_10_0-1160_21_1-debuginfo` Red Hat:enterprise_linux:7::server	All versions	`0:1-3.el7`
`kpatch-patch-3_10_0-1160_24_1` Red Hat:enterprise_linux:7::server	All versions	`0:1-1.el7`
`kpatch-patch-3_10_0-1160_24_1-debuginfo` Red Hat:enterprise_linux:7::server	All versions	`0:1-1.el7`
`kpatch-patch-3_10_0-1160_25_1` Red Hat:enterprise_linux:7::server	All versions	`0:1-1.el7`
`kpatch-patch-3_10_0-1160_25_1-debuginfo` Red Hat:enterprise_linux:7::server	All versions	`0:1-1.el7`
`kpatch-patch-3_10_0-1160_2_1` Red Hat:enterprise_linux:7::server	All versions	`0:1-6.el7`
`kpatch-patch-3_10_0-1160_2_1-debuginfo` Red Hat:enterprise_linux:7::server	All versions	`0:1-6.el7`
`kpatch-patch-3_10_0-1160_2_2` Red Hat:enterprise_linux:7::server	All versions	`0:1-6.el7`
`kpatch-patch-3_10_0-1160_2_2-debuginfo` Red Hat:enterprise_linux:7::server	All versions	`0:1-6.el7`
`kpatch-patch-3_10_0-1160_6_1` Red Hat:enterprise_linux:7::server	All versions	`0:1-6.el7`
`kpatch-patch-3_10_0-1160_6_1-debuginfo` Red Hat:enterprise_linux:7::server	All versions	`0:1-6.el7`

Products include Debian Debian Linux, Fedoraproject Fedora, Linux kernel.

How do I fix CVE-2021-3347?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2021-3347 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-3347 exists.

Public exploit code: 1 proofs of concept on GitHub.

All Debian Debian Linux vulnerabilities

Sources

Also known as A-171705902, ASB-A-171705902, DEBIAN-CVE-2021-3347, GHSA-8r42-h5pm-2vw2, MGASA-2021-0062, RHSA-2021:2285 and 1 more.