Inefficient regular expression complexity in Fluentd - CVE-2021-41186
Published: October 29, 2021 / Updated: June 29, 2026
Vulnerability identifier: #VU135826
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2021-41186
CWE-ID: CWE-1333
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Fluentd Project
Affected software:
Fluentd
Fluentd
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to improper input validation in parser_apache2 when parsing broken apache log entries containing a certain string pattern. A remote attacker can supply a specially crafted log entry to cause a denial of service.
How to mitigate CVE-2021-41186
Install security update from vendor's website.