CVE-2021-41186

low-risk

Published 2021-10-29

Fluentd collects events from various data sources and writes them to files to help unify logging infrastructure. The 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. This issue is patched in version 1.14.2 There are two workarounds available. Either don't use parser_apache2 for parsing logs (which cannot guarantee generated by Apache), or 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).

Do I need to act?

0.49% chance of exploitation

EPSS score — low exploit probability

Not on CISA KEV list

No confirmed active exploitation reported to CISA

Patch status unknown

Check vendor advisories for fix availability and mitigation guidance

CVSS 5.9/10 Medium

NETWORK / HIGH complexity

Affected Products (1)

Fluentd

Affected Vendors

Fluentd

References (6)

Release Notes https://github.com/fluent/fluentd/blob/master/CHANGELOG.md#v1142

Third Party Advisory https://github.com/fluent/fluentd/security/advisories/GHSA-hwhf-64mh-r662

Broken Link https://github.com/github/securitylab-vulnerabilities/blob/52dc4a2a828c6dc242319...

Release Notes https://github.com/fluent/fluentd/blob/master/CHANGELOG.md#v1142

Third Party Advisory https://github.com/fluent/fluentd/security/advisories/GHSA-hwhf-64mh-r662

Broken Link https://github.com/github/securitylab-vulnerabilities/blob/52dc4a2a828c6dc242319...

/ 100

low-risk

Severity 18/34 · Moderate

Exploitability 2/34 · Minimal

Exposure 5/34 · Minimal