{"id":"CVE-2021-41186","aliases":["BIT-fluentd-2021-41186","GHSA-hwhf-64mh-r662"],"url":"https://o3.security/vulnerability/CVE-2021-41186","summary":"ReDoS vulnerability in parser_apache2","details":"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).","published":"2021-10-29T14:15:07.730Z","modified":"2026-07-09T11:34:06.087734Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":{"score":0.02196,"percentile":0.80938,"asOf":"2026-08-23"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"RubyGems","name":"fluentd","fixedVersion":"1.14.2"}],"fix":{"url":"https://github.com/fluent/fluentd/commit/5482a3d049dab351de0be68f4b4bc562319d8511","label":"fluent/fluentd@5482a3d"},"references":[{"type":"WEB","url":"https://github.com/github/securitylab-vulnerabilities/blob/52dc4a2a828c6dc24231967c2937ad92038184a9/vendor_reports/GHSL-2021-102-fluent-fluentd.md"},{"type":"ADVISORY","url":"https://github.com/fluent/fluentd/blob/master/CHANGELOG.md#v1142"},{"type":"ADVISORY","url":"https://github.com/fluent/fluentd/security/advisories/GHSA-hwhf-64mh-r662"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-41186"},{"type":"WEB","url":"https://github.com/fluent/fluentd/commit/5482a3d049dab351de0be68f4b4bc562319d8511"},{"type":"PACKAGE","url":"https://github.com/fluent/fluentd"},{"type":"WEB","url":"https://github.com/rubysec/ruby-advisory-db/blob/master/gems/fluentd/CVE-2021-41186.yml"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-09T11:34:06.087734Z"}}