CVE-2021-21900 Use after free in LibreCAD

What is CVE-2021-21900?

CVE-2021-21900 is a high-severity use after free vulnerability in Debian Debian Linux, published on 19 Nov 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 code execution vulnerability exists in the dxfRW::processLType() functionality of LibreCad libdxfrw 2.2.0-rc2-19-ge02f3580. A specially-crafted .dxf file can lead to a use-after-free vulnerability. An attacker can provide a malicious file to trigger this vulnerability.

Weakness: CWE-416

Which versions are affected by CVE-2021-21900?

It affects 3 products.

Products include Debian Debian Linux, Fedoraproject Fedora, Librecad Libdxfrw.

How do I fix CVE-2021-21900?

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-2021-21900 being exploited?

There is no known exploitation of CVE-2021-21900 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-2021-21900, GHSA-j7ww-g7m2-fpcg, UBUNTU-CVE-2021-21900.