SB20261109108 - Inefficient regular expression complexity in pymdown-extensions

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Main Vulnerability Database SB20261109108

SB20261109108 - Inefficient regular expression complexity in pymdown-extensions

Published: November 9, 2026

Security Bulletin ID SB20261109108
CSH Severity
Medium
Patch available
YES
Number of vulnerabilities 1
Exploitation vector Remote access
Highest impact Denial of service

Breakdown by Severity

Medium 100%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 1 vulnerability.


1) Inefficient regular expression complexity (CVE-ID: N/A)

CWE-ID: CWE-1333 - Inefficient Regular Expression Complexity

CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]


The vulnerability allows an unauthenticated remote attacker to exhaust rendering workers and deny service in downstream applications using pymdown-extensions.

The vulnerability exists due to quadratic regular expression processing of crafted Markdown in explicitly enabled pymdownx.tilde or pymdownx.caret extensions using default smart processing. An unauthenticated remote attacker can submit repeated requests containing crafted delimiter sequences to services synchronously rendering untrusted Markdown without input-size or rendering-time limits, consuming excessive CPU.


Remediation

Install update from vendor's website.

References