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Vulnerability · Published Oct 29, 2021 · Assigned by GitHub_M

CVE-2021-41186ReDoS vulnerability in parser_apache2

Medium 5.9

In plain English

A medium-severity uncontrolled resource consumption in fluentd from fluent. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 2.2% (higher than 83% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.9Medium
Exploit odds (30 days)2.2%top 17.3% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack toolingNoneno public tooling known

Official description

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).

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
RubyGemsfluentd1.14.2GHSA-hwhf-64mh-r662

Affected products (as reported)

VendorProductVersions
fluent fluentd >= 0.14.14, < 1.14.2

Weakness: CWE-400 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

References