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Vulnerability record · CVE-2021-20270 · published 23 March 2021

CVE-2021-20270: Pygments vulnerability

Pygments · Pygments

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.

7.5 CVSS 3.1 High EPSS 2.8% · top 14.3% CWE-835 · CWE-835
7.5CVSS 3.1 base score, v2 5.0
2.8%EPSS exploitation probability, 30 days
NoNot in CISA KEV
7Affected product versions listed by NVD
10References
17 Jun 2026Last modified by NVD

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.

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

Affected products

7 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://bugzilla.redhat.com/show_bug.cgi?id=1922136 Issue TrackingPatchThird Party Advisory
https://lists.debian.org/debian-lts-announce/2021/05/msg00003.html Mailing ListThird Party Advisory
https://lists.debian.org/debian-lts-announce/2021/05/msg00006.html Mailing ListThird Party Advisory
https://www.debian.org/security/2021/dsa-4889 Third Party Advisory
https://www.oracle.com/security-alerts/cpuoct2021.html Not ApplicableThird Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1922136 Issue TrackingPatchThird Party Advisory
https://lists.debian.org/debian-lts-announce/2021/05/msg00003.html Mailing ListThird Party Advisory
https://lists.debian.org/debian-lts-announce/2021/05/msg00006.html Mailing ListThird Party Advisory
https://www.debian.org/security/2021/dsa-4889 Third Party Advisory
https://www.oracle.com/security-alerts/cpuoct2021.html Not ApplicableThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-20270), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.