SB2026081973 - Inefficient regular expression complexity in Twisted Web

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Main Vulnerability Database SB2026081973

SB2026081973 - Inefficient regular expression complexity in Twisted Web

Published: August 19, 2026

Security Bulletin ID SB2026081973
CSH Severity
Low
Patch available
YES
Number of vulnerabilities 1
Exploitation vector Remote access
Highest impact Partial DoS

Breakdown by Severity

Low 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: 5.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]


The vulnerability allows a remote user to cause a denial of service.

The vulnerability exists due to inefficient regular expression complexity in the wildcardToRegexp() function in twisted/mail/imap4.py when processing IMAP wildcard patterns in LIST or LSUB commands. A remote user can send a specially crafted quoted pattern string containing catastrophic-backtracking regex syntax to cause a denial of service.

Because the server uses a cooperative single-threaded reactor, a blocking regex match can freeze all I/O on the server for the duration of the match.


Remediation

Install update from vendor's website.

References