Denial of Service Vulnerability in Pygments from Python Lexers
CVE-2026-4539

4.8MEDIUM

Key Information:

Vendor

Pygments

Status
Pygments
Vendor
CVE Published:
22 March 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-4539?

A security flaw exists in the Pygments library, specifically within the AdlLexer function found in pygments/lexers/archetype.py. This vulnerability leads to inefficient regular expression processing, potentially allowing a local attacker to execute denial of service attacks. Although the issue was reported early to the Pygments team, there has been no acknowledgment or response regarding a fix. As a result, the exploit is publicly available, posing a risk for users with local access to the vulnerable versions.

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Affected Version(s)

pygments 2.19.0

pygments 2.19.1

pygments 2.19.2

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2026-4539 - Proof of Concept

References

https://vuldb.com/?id.352327
vdb-entrytechnical-description
https://vuldb.com/?ctiid.352327
signaturepermissions-required
https://vuldb.com/?submit.774685
third-party-advisory

CVSS V4

Score:
4.8
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
Low
Attack Vector:
Local
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

ybdesire (VulDB User)
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