CVE-2020-21688 Use after free in n/a

What is CVE-2020-21688?

CVE-2020-21688 is a high-severity use after free vulnerability in Debian Debian Linux, published on 10 Aug 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

A heap-use-after-free in the av_freep function in libavutil/mem.c of FFmpeg 4.2 allows attackers to execute arbitrary code.

Weakness: CWE-416

Which versions are affected by CVE-2020-21688?

It affects 2 products.

Products include Debian Debian Linux, Ffmpeg Ffmpeg.

How do I fix CVE-2020-21688?

Upgrade to a fixed version.

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-2020-21688 being exploited?

There is no known exploitation of CVE-2020-21688 in the wild and no public exploit code.

Other vulnerabilities in Debian Debian Linux

• CVE-2015-3306 ProFTPD Improper Access Control Exploited Critical 10.0
• CVE-2025-49113 RoundCube Webmail Deserialization of Untrusted Data Exploited Critical 9.9
• CVE-2026-24061 GNU InetUtils Argument Injection Exploited Critical 9.8
• CVE-2025-39682 Linux Kernel Improper Check for Unusual or Exceptional Conditions Exploited Critical 9.8
• CVE-2024-9680 Mozilla Firefox Use-After-Free Exploited Critical 9.8

All Debian Debian Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2020-21688, GHSA-mjfr-374m-86mh, UBUNTU-CVE-2020-21688.