🛡️ CVE-2026-4539 — pygments

🟢 CVSS 3.3 — Low ✅ No Known Exploit CWE-1333 NVD
3.3
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Pygments has Regular Expression Denial of Service (ReDoS) due to Inefficient Regex for GUID Matching

A security flaw has been discovered in pygments before 2.20.0. The impacted element is the function AdlLexer of the file pygments/lexers/archetype.py. The manipulation results in inefficient regular expression complexity. The attack is only possible with local access. The exploit has been released to the public and may be used for attacks. The project was informed of the problem early through an issue report but has not responded yet.

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability low.

Weakness class

CVE-2026-4539 is classified as CWE-1333: Inefficient Regular Expression Complexity. A regular expression backtracks catastrophically on crafted input, consuming CPU out of proportion to input size.

Affected software

CVE-2026-4539 is recorded against 2 packages.

  • pygments (fixed in 2.20.0)
  • unknown

Timeline and source

Published on 22 March 2026 and last revised on 13 July 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

nvd.nist.gov (Advisory)
github.com (Web)
github.com (Web)
github.com (Web)
github.com (Package)
github.com (Web)
vuldb.com (Web)
vuldb.com (Web)
vuldb.com (Web)

CVE-2026-4539 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity LOW
CVSS Score 3.3
CVSS Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
CWE CWE-1333
Public Exploit ✅ No
Source NVD
Published 2026-03-22
Updated 2026-08-12
Modified 2026-07-13
Fix URL N/A

Affected Packages

Software From version Fixed in
pygments — 2.20.0
unknown — —

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