What’s Vulnerable › Vulnerabilities

CVE-2021-21236: Regular Expression Denial of Service in CairoSVG

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-01-06 · updated 2026-06-17
• Weakness: CWE-400

Description

CairoSVG is a Python (pypi) package. CairoSVG is an SVG converter based on Cairo. In CairoSVG before version 2.5.1, there is a regular expression denial of service (REDoS) vulnerability. When processing SVG files, the python package CairoSVG uses two regular expressions which are vulnerable to Regular Expression Denial of Service (REDoS). If an attacker provides a malicious SVG, it can make cairosvg get stuck processing the file for a very long time. This is fixed in version 2.5.1. See Referenced GitHub advisory for more information.

Affected products

• Kozea CairoSVG: before 2.5.1 — fixed in 2.5.1

How to fix

Upgrade to a fixed version: Kozea CairoSVG 2.5.1. Check the vendor advisory for mitigations.

References

• https://github.com/Kozea/CairoSVG/commit/cfc9175e590531d90384aa88845052de53d94bf3
• https://github.com/Kozea/CairoSVG/releases/tag/2.5.1
• https://github.com/Kozea/CairoSVG/security/advisories/GHSA-hq37-853p-g5cf
• https://pypi.org/project/CairoSVG/
• https://github.com/Kozea/CairoSVG/commit/cfc9175e590531d90384aa88845052de53d94bf3
• https://github.com/Kozea/CairoSVG/releases/tag/2.5.1
• https://github.com/Kozea/CairoSVG/security/advisories/GHSA-hq37-853p-g5cf
• https://pypi.org/project/CairoSVG/

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