SB2026100181 - Inefficient regular expression complexity in Fail2ban

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Main Vulnerability Database SB2026100181

SB2026100181 - Inefficient regular expression complexity in Fail2ban

Published: October 1, 2026

Security Bulletin ID SB2026100181
CSH Severity
Medium
Patch available
YES
Number of vulnerabilities 1
Exploitation vector Remote access
Highest impact Partial DoS

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


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

The vulnerability exists due to inefficient regular expression complexity in the shared RFC5424 __prefix_line regex in common.conf when processing RFC5424 log lines containing unterminated structured-data fields. A remote attacker can inject a crafted RFC5424 log line to cause a denial of service.

Only filters configured with logtype=rfc5424 are affected.


Remediation

Install update from vendor's website.

References