CVE-2021-20270

Name: CVE-2021-20270
Creator: NVD / NIST
Published: 2021-03-23T17:15:13.827+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 2.71%

Last modified Jun 17, 2026

CVE-2021-20270 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. An infinite loop in SMLLexer in Pygments versions 1.5 to 2.7.3 may lead to denial of service when performing syntax highlighting of a Standard ML (SML) source file, as demonstrated by input that only contains the "exception" keyword.. EPSS estimates a 2.71% chance of exploitation in the next 30 days.

Description

An infinite loop in SMLLexer in Pygments versions 1.5 to 2.7.3 may lead to denial of service when performing syntax highlighting of a Standard ML (SML) source file, as demonstrated by input that only contains the "exception" keyword.

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

2.71%

84.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Pygments	Pygments	>= 1.5, <= 2.7.3
Redhat	Openshift Container Platform	3.11
Redhat	Openshift Container Platform	4.0
Redhat	Openstack Platform	10.0
Redhat	Software Collections	All versions
Redhat	Enterprise Linux	7.0
Redhat	Enterprise Linux	8.0
Fedoraproject	Fedora	33
Debian	Debian Linux	9.0
Debian	Debian Linux	10.0

References

https://bugzilla.redhat.com/show_bug.cgi?id=1922136Issue Tracking, Patch, 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://www.debian.org/security/2021/dsa-4889Third Party Advisory
https://www.oracle.com/security-alerts/cpuoct2021.htmlNot Applicable, Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1922136Issue Tracking, Patch, 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://www.debian.org/security/2021/dsa-4889Third Party Advisory
https://www.oracle.com/security-alerts/cpuoct2021.htmlNot Applicable, Third Party Advisory

Timeline

Published: Mar 23, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-20270?

How severe is CVE-2021-20270?

CVE-2021-20270 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 2.71% probability of exploitation in the next 30 days.

How do I fix CVE-2021-20270?

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-2021-20270?

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

Scan your code now

Source: NVD / NIST