CVE-2021-20270
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (2.76%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 2.76% probability · 86th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-835
- Affected
- pygments/pygments · redhat/openshift container platform · redhat/openstack platform · redhat/software collections · redhat/enterprise linux · fedoraproject/fedora · debian/debian linux
- Source
- secalert@redhat.com
EPSS 2.8% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
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
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.