CVE-2021-20309 Denial of service in ImagemMagick

What is CVE-2021-20309?

CVE-2021-20309 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 11 May 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

A flaw was found in ImageMagick in versions before 7.0.11 and before 6.9.12, where a division by zero in WaveImage() of MagickCore/visual-effects.c may trigger undefined behavior via a crafted image file submitted to an application using ImageMagick. The highest threat from this vulnerability is to system availability.

Weakness: CWE-369

Which versions are affected by CVE-2021-20309?

It affects 2 products.

Products include Debian Debian Linux, Imagemagick Imagemagick.

How do I fix CVE-2021-20309?

Upgrade to a fixed version.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2021-20309 being exploited?

There is no known exploitation of CVE-2021-20309 in the wild and no public exploit code.

Other vulnerabilities in Debian Debian Linux

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• 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-2021-20309, GHSA-vfcg-3f47-8mgm, JLSEC-2026-884, UBUNTU-CVE-2021-20309.