Resource exhaustion in Fluent Fluentd
CVE-2021-41186
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).
Vulnerability class: DoS (Denial of Service)
EPSS: 0.022 (81.3th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.
Affected products
- Fluent Fluentd — versions >= 0.14.14, < 1.14.2
- Fluentd
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Third Party Advisory)
- security-advisories@github.com (Third Party Advisory, x_refsource_MISC, Release Notes)
- security-advisories@github.com (x_refsource_MISC, Broken Link)
Frequently asked questions
- What is CVE-2021-41186?
- CVE-2021-41186 is a medium-severity vulnerability in Fluent Fluentd, classified under Uncontrolled Resource Consumption. CVSS score: 5.9/10. Published 2021-10-29.
- How severe is CVE-2021-41186?
- Medium severity. CVSS v3 base score is 5.9 out of 10.