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NVD / CVE Program· CNA mitre

CVE-2021-27291: In pygments 1.1+, fixed in 2.7.4, the lexers used to parse programming languages rely heavily on regular expressions.

Noroxi assessment

Priority: Monitor (action score 31/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 3.9% (FIRST EPSS); higher than 90.3% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: n/a n/a 2.7.4.

Low priority for now. Upgrade to n/a n/a 2.7.4 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Mar 17, 2021
Updated
Jun 16, 2026
EPSS
3.9% · 90th percentile

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 3.9%

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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  • when exploit code appears or is weaponized
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  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
pygmentspygments
debiandebian linux
fedoraprojectfedora

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux10.0
  • debian debian linux9.0
  • fedoraproject fedora32
  • fedoraproject fedora33
  • pygments pygments1.1 and later · before 2.7.4

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8babelbefore 2.5.1-10.module_el8.6.0+2781+fed64c132.5.1-10.module_el8.6.0+2781+fed64c13
AlmaLinux:8python-nose-docsbefore 1.3.7-31.module_el8.5.0+2569+5c5719bc1.3.7-31.module_el8.5.0+2569+5c5719bc
AlmaLinux:8python-nose-docsbefore 1.3.7-31.module_el8.6.0+2781+fed64c131.3.7-31.module_el8.6.0+2781+fed64c13
AlmaLinux:8python-psycopg2-docbefore 2.7.5-7.module_el8.6.0+2781+fed64c132.7.5-7.module_el8.6.0+2781+fed64c13
AlmaLinux:8python-pymongo-docbefore 3.7.0-1.module_el8.5.0+135+5ce32bc43.7.0-1.module_el8.5.0+135+5ce32bc4
AlmaLinux:8python-pymongo-docbefore 3.7.0-1.module_el8.5.0+2569+5c5719bc3.7.0-1.module_el8.5.0+2569+5c5719bc
AlmaLinux:8python-sqlalchemy-docbefore 1.3.2-2.module_el8.6.0+2781+fed64c131.3.2-2.module_el8.6.0+2781+fed64c13
AlmaLinux:8python-sqlalchemy-docbefore 1.3.2-2.module_el8.5.0+2569+5c5719bc1.3.2-2.module_el8.5.0+2569+5c5719bc
AlmaLinux:8python-virtualenv-docbefore 15.1.0-21.module_el8.5.0+2569+5c5719bc15.1.0-21.module_el8.5.0+2569+5c5719bc
AlmaLinux:8python-virtualenv-docbefore 15.1.0-21.module_el8.5.0+135+5ce32bc415.1.0-21.module_el8.5.0+135+5ce32bc4
AlmaLinux:8python2-attrsbefore 17.4.0-10.module_el8.6.0+2781+fed64c1317.4.0-10.module_el8.6.0+2781+fed64c13
AlmaLinux:8python2-babelbefore 2.5.1-10.module_el8.6.0+2781+fed64c132.5.1-10.module_el8.6.0+2781+fed64c13
AlmaLinux:8python2-backportsbefore 1.0-16.module_el8.6.0+2781+fed64c131.0-16.module_el8.6.0+2781+fed64c13
AlmaLinux:8python2-backports-ssl_match_hostnamebefore 3.5.0.1-12.module_el8.6.0+2781+fed64c133.5.0.1-12.module_el8.6.0+2781+fed64c13
AlmaLinux:8python2-bsonbefore 3.7.0-1.module_el8.6.0+2781+fed64c133.7.0-1.module_el8.6.0+2781+fed64c13
AlmaLinux:8python2-chardetbefore 3.0.4-10.module_el8.6.0+2781+fed64c133.0.4-10.module_el8.6.0+2781+fed64c13
AlmaLinux:8python2-coveragebefore 4.5.1-4.module_el8.6.0+2781+fed64c134.5.1-4.module_el8.6.0+2781+fed64c13
AlmaLinux:8python2-Cythonbefore 0.28.1-7.module_el8.6.0+2781+fed64c130.28.1-7.module_el8.6.0+2781+fed64c13
AlmaLinux:8python2-dnsbefore 1.15.0-10.module_el8.6.0+2781+fed64c131.15.0-10.module_el8.6.0+2781+fed64c13
AlmaLinux:8python2-docsbefore 2.7.16-2.module_el8.6.0+2781+fed64c132.7.16-2.module_el8.6.0+2781+fed64c13
AlmaLinux:8python2-docs-infobefore 2.7.16-2.module_el8.6.0+2781+fed64c132.7.16-2.module_el8.6.0+2781+fed64c13
AlmaLinux:8python2-docutilsbefore 0.14-12.module_el8.6.0+2781+fed64c130.14-12.module_el8.6.0+2781+fed64c13
AlmaLinux:8python2-funcsigsbefore 1.0.2-13.module_el8.6.0+2781+fed64c131.0.2-13.module_el8.6.0+2781+fed64c13
AlmaLinux:8python2-idnabefore 2.5-7.module_el8.6.0+2781+fed64c132.5-7.module_el8.6.0+2781+fed64c13

+96

Same product

pygments: all records

Other highest-scoring records for the same primary product.

  • CVE-2015-8557The FontManager._get_nix_font_path function in formatters/img.py in Pygments 1.2.2 through 2.0.2 allows remote attackers to execute arbitrar
    38Monitor
  • CVE-2021-20270An 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 Standa
    31Monitor
  • CVE-2022-40896A ReDoS issue was discovered in pygments/lexers/smithy.py in pygments through 2.15.0 via SmithyLexer.
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
n/a n/a2.7.4 · descriptionVendor (CNA)
almalinux:python-nose-docs1.3.7-31.module_el8.6.0+2781+fed64c13 · AlmaLinux:8Package registry (OSV)
almalinux:python-pymongo-doc3.7.0-1.module_el8.5.0+135+5ce32bc4 · AlmaLinux:8Package registry (OSV)
almalinux:python-sqlalchemy-doc1.3.2-2.module_el8.6.0+2781+fed64c13 · AlmaLinux:8Package registry (OSV)
almalinux:python-virtualenv-doc15.1.0-21.module_el8.5.0+2569+5c5719bc · AlmaLinux:8Package registry (OSV)
almalinux:python3-bson3.7.0-1.module_el8.5.0+135+5ce32bc4 · AlmaLinux:8Package registry (OSV)
almalinux:python3-distro1.4.0-2.module_el8.5.0+135+5ce32bc4 · AlmaLinux:8Package registry (OSV)
almalinux:python3-docs3.6.7-2.module_el8.5.0+2569+5c5719bc · AlmaLinux:8Package registry (OSV)
almalinux:python3-PyMySQL0.10.1-2.module_el8.5.0+2569+5c5719bc · AlmaLinux:8Package registry (OSV)
almalinux:resource-agents4.1.1-98.el8 · AlmaLinux:8Package registry (OSV)
almalinux:resource-agents-aliyun4.1.1-98.el8 · AlmaLinux:8Package registry (OSV)
almalinux:resource-agents-gcp4.1.1-98.el8 · AlmaLinux:8Package registry (OSV)
almalinux:resource-agents-paf4.1.1-98.el8 · AlmaLinux:8Package registry (OSV)
alpine:py3-pygments2.5.2-r1 · Alpine:v3.11Package registry (OSV)
debian:mediawiki1:1.35.2-1 · Debian:12Package registry (OSV)
debian:pygments2.7.1+dfsg-2.1 · Debian:12Package registry (OSV)
opensuse:python-Pygments2.6.1-lp152.5.12.1 · openSUSE:Leap 15.2Package registry (OSV)
PyPI:pygments2.7.4Package registry (OSV)
red hat:automation-hub0:4.2.2-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python-bleach0:3.3.0-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python-bleach-allowlist0:1.0.3-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python-galaxy-importer0:0.2.15-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python-galaxy-ng0:4.2.2-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python-pulp-ansible1:0.5.6-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python3-bleach0:3.3.0-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python3-bleach-allowlist0:1.0.3-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python3-django0:2.2.18-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python3-galaxy-importer0:0.2.15-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python3-galaxy-ng0:4.2.2-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python3-pulp-ansible1:0.5.6-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)

+13

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-1333 · Inefficient Regular Expression Complexity

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records