CVE-2021-20270: debian debian_linux Loop with Unreachable Exit Condition
Vulnerability summary
CVE-2021-20270 is a high (CVSS 7.5) Loop with Unreachable Exit Condition vulnerability in debian debian_linux. EPSS estimates a 2.76% chance of exploitation in the next 30 days, higher than 86.2% of scored vulnerabilities.
Severe, CVSS 7.5 (NVD); no exploitation reported by the 5 checked sources; EPSS 3% (FIRST, 03-11-2026)
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 9 · Related 1Timeline
- 23-03-2021PublishedVulnerability first disclosed.
- 03-08-2024Last modifiedVulnerability information updated.
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 metrics
7 scores · 5 sources · 3 versions- OSV · AlpineEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · PypiEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
2.76%
Chance of exploitation in the next 30 days
Percentile
86%
Versus all other CVEs
30-day change
No change 0.00 pp
From 2.76% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Suse13 products
- python-Pygments&distro=SUSE Enterprise Storage 6< 2.6.1-7.7.1
- python-Pygments&distro=SUSE Linux Enterprise High Performance Computing 15 SP1-ESPOS< 2.6.1-7.7.1
- python-Pygments&distro=SUSE Linux Enterprise High Performance Computing 15 SP1-LTSS< 2.6.1-7.7.1
- python-Pygments&distro=SUSE Linux Enterprise High Performance Computing 15-ESPOS< 2.2.0-4.6.1
- python-Pygments&distro=SUSE Linux Enterprise High Performance Computing 15-LTSS< 2.2.0-4.6.1
Redhat4 products
- enterprise_linuxEOL7.0 | 8.0
- openshift_container_platform3.11 | 4.0
- openstack_platform10.0
- software_collectionsna
Debian3 products
- mediawiki< 1:1.35.2-1
- pygments< 2.3.1+dfsg-1+deb10u1 | < 2.2.0+dfsg-1+deb9u1 | < 2.7.1+dfsg-2
- debian_linuxEOL9.0 | 10.0
Opensuse2 products
- python-Pygments&distro=openSUSE Leap 15.2< 2.6.1-lp152.5.9.1
- python-Pygments&distro=openSUSE Tumbleweed< 2.21.0-1.1
Alpine1 product
- py3-pygments< 2.7.4-r0
Fedoraproject1 product
- fedoraEOL33
Pygments1 product
- pygments≥ 1.5, ≤ 2.7.3
PyPI1 product
- pygments≥ 1.5, < 2.7.4
Ubuntu1 product
- pygments< 1.6+dfsg-1ubuntu1.1+esm1 | < 2.1+dfsg-1ubuntu0.1 | < 2.2.0+dfsg-1ubuntu0.1 | < 2.3.1+dfsg-1ubuntu2.1
9 vendors · 27 products
References
21 links- bugzilla.redhat.com/show_bug.cgi?id=1922136X Refsource MISCWEBREPORTIssue TrackingPatchThird Party Advisory
www.debian.org/security/2021/dsa-4889Vendor AdvisoryX Refsource DEBIANWEBAdvisoryThird Party Advisory- lists.debian.org/debian-lts-announce/2021/05/msg00003.htmlMailing ListX Refsource MLISTWEBThird Party Advisory
- lists.debian.org/debian-lts-announce/2021/05/msg00006.htmlMailing ListX Refsource MLISTWEBThird Party Advisory
Show all 21 references
- github.com/pygments/pygmentsPACKAGE
- lists.opensuse.org/archives/…Advisory