Vulnerability in fluentd (CVE-2021-41186)
Summary
Vulnerability in fluentd (CVE-2021-41186). Risk of unauthorized operations or information disclosure. Exploitable via FLUENT_PLUGIN. Mitigation: upgrade to 1.14.2 or later.
Original description
The description as published by the source.
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).
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2021-41186 has been found in fluentd.
Attackers can target a specific entry point like FLUENT_PLUGIN over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade fluentd to 1.14.2 or later.
If unsure, ask your IT team or search "fluentd CVE-2021-41186" on the vendor's site.
CVE-2021-41186 (fluentd) — CWE-400
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: FLUENT_PLUGIN
Patched: 1.14.2 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-400) exists in fluentd. Attackers reach the vulnerable code path via FLUENT_PLUGIN without authentication.
Check the vendor advisory for the affected versions of fluentd. Attack surface: FLUENT_PLUGIN.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 1.14.2.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'fluentd' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'fluentd' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
fluentdを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade fluentd to 1.14.2ステージング環境で 1.14.2 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory github.com
- advisory github.com
- package github.com
- web nvd.nist.gov
- web github.com
- web github.com
- web github.com