CVE-2021-27291

Name: CVE-2021-27291
Creator: NVD / NIST
Published: 2021-03-17T13:15:15.137+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 3.83%

Last modified Jun 17, 2026

CVE-2021-27291 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. In pygments 1.1+, fixed in 2.7.4, the lexers used to parse programming languages rely heavily on regular expressions. Some of the regular expressions have exponential or cubic worst-case complexity and are vulnerable to ReDoS. EPSS estimates a 3.83% chance of exploitation in the next 30 days.

Description

In pygments 1.1+, fixed in 2.7.4, the lexers used to parse programming languages rely heavily on regular expressions. Some of the regular expressions have exponential or cubic worst-case complexity and are vulnerable to ReDoS. By crafting malicious input, an attacker can cause a denial of service.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

3.83%

88.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-1333

Affected Software

Vendor	Product	Versions
Pygments	Pygments	>= 1.1, < 2.7.4
Debian	Debian Linux	9.0
Debian	Debian Linux	10.0
Fedoraproject	Fedora	32
Fedoraproject	Fedora	33

References

https://gist.github.com/b-c-ds/b1a2cc0c68a35c57188575eb496de5ceExploit, Third Party Advisory
https://github.com/pygments/pygments/commit/2e7e8c4a7b318f4032493773732754e418279a14Patch, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/03/msg00024.htmlMailing List, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/05/msg00003.htmlMailing List, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/05/msg00006.htmlMailing List, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GSJRFHALQ7E3UV4FFMFU2YQ6LUDHAI55/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WSLD67LFGXOX2K5YNESSWAS4AGZIJTUQ/
https://www.debian.org/security/2021/dsa-4878Third Party Advisory
https://www.debian.org/security/2021/dsa-4889Third Party Advisory
https://gist.github.com/b-c-ds/b1a2cc0c68a35c57188575eb496de5ceExploit, Third Party Advisory
https://github.com/pygments/pygments/commit/2e7e8c4a7b318f4032493773732754e418279a14Patch, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/03/msg00024.htmlMailing List, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/05/msg00003.htmlMailing List, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/05/msg00006.htmlMailing List, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GSJRFHALQ7E3UV4FFMFU2YQ6LUDHAI55/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WSLD67LFGXOX2K5YNESSWAS4AGZIJTUQ/
https://www.debian.org/security/2021/dsa-4878Third Party Advisory
https://www.debian.org/security/2021/dsa-4889Third Party Advisory

Timeline

Published: Mar 17, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-27291?

How severe is CVE-2021-27291?

CVE-2021-27291 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 3.83% probability of exploitation in the next 30 days.

How do I fix CVE-2021-27291?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-27291?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST