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ReDoS vulnerability in parser_apache2

Moderate severity GitHub Reviewed Published Oct 29, 2021 in fluent/fluentd • Updated May 4, 2023

Package

bundler fluentd (RubyGems)

Affected versions

>= 0.14.14, < 1.14.2

Patched versions

1.14.2

Description

Impact

parser_apache2 plugin in Fluentd v0.14.14 to v1.14.1 suffers from a regular expression denial of service (ReDoS) vulnerability. A broken apache log with a certain pattern of string can spend too much time in a regular expression, resulting in the potential for a DoS attack.

Patches

v1.14.2

Workarounds

Either of the following:

  • Don't use parser_apache2 for parsing logs which cannot guarantee generated by Apache.
  • Put patched version of parser_apache2.rb into /etc/fluent/plugin directory (or any other directories specified by the environment variable FLUENT_PLUGIN or --plugin option of fluentd).

References

References

@ashie ashie published to fluent/fluentd Oct 29, 2021
Reviewed Oct 29, 2021
Published by the National Vulnerability Database Oct 29, 2021
Published to the GitHub Advisory Database Nov 1, 2021
Last updated May 4, 2023

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS score

0.252%
(66th percentile)

Weaknesses

CVE ID

CVE-2021-41186

GHSA ID

GHSA-hwhf-64mh-r662

Source code

Credits

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