Path Traversal in Logback-classic (CVE-2026-104721)
Summary
Path traversal in Logback-classic (CVE-2026-104721). Risk of unauthorized operations or information disclosure.
Original description
The description as published by the source.
Path-traversal vulnerability in QOS.CH Sarl Logback-classic on Java (logback-classic module) allows path-traversal vulnerability. More specifically, an
MDC-based discriminator value flows unsanitized into a nested
FileAppender path, letting an attacker who influences that MDC value
(e.g. via an HTTP header)
create and append log files outside the intended directory.
This issue affects Logback-classic: from 0.9.14 through 1.6.4. This vulnerability is similar to CVE-2026-19880 but involves other attack techniques.
Source: NIST National Vulnerability Database NVD GitHub Advisory
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-2026-104721 has been found in Logback-classic.
Risk of unauthorized operations or information disclosure.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Logback-classic CVE-2026-104721" on the vendor's site.
CVE-2026-104721 (Logback-classic) — CWE-22
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.
Path traversal (CWE-22) exists in Logback-classic.
Check the vendor advisory for the affected versions of Logback-classic.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to the patched release per vendor advisory.
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 'Logback-classic' . 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
-
1Identify exposure identify
grep -r 'Logback-classic' . | 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
Logback-classicを grep し、稼働しているサービス・バージョンを把握する。 -
2Post-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。
References
- web logback.qos.ch
- web nvd.nist.gov
- web github.com