CVE-2021-3405 Memory corruption in libebml

What is CVE-2021-3405?

CVE-2021-3405 is a medium-severity memory corruption vulnerability in Debian Debian Linux, published on 23 Feb 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 flaw was found in libebml before 1.4.2. A heap overflow bug exists in the implementation of EbmlString::ReadData and EbmlUnicodeString::ReadData in libebml.

Weakness: CWE-787

Which versions are affected by CVE-2021-3405?

It affects 3 products.

Products include Debian Debian Linux, Fedoraproject Fedora, Matroska Libebml.

How do I fix CVE-2021-3405?

Upgrade to a fixed version.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2021-3405 being exploited?

There is no known exploitation of CVE-2021-3405 in the wild and no public exploit code.

Other vulnerabilities in Debian Debian Linux

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• 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-2021-3405, DLA-2629-1, GHSA-xc72-rxv8-3m23, MGASA-2021-0226, MGASA-2021-0338, UBUNTU-CVE-2021-3405 and 1 more.