ADVISORIES

• CVE-2021-41186 (NVD)
• GHSA-hwhf-64mh-r662
• Vendor Advisory

GEM

fluentd

SEVERITY

CVSS v3.x: 5.9 (Medium)

UNAFFECTED VERSIONS

• < 0.14.14

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).

RELATED

• https://securitylab.github.com/advisories/GHSL-2021-102-fluent-fluentd/
• https://github.com/fluent/fluentd/blob/master/CHANGELOG.md#v1142