https://www.phllaps.net/tags/onlyoffice/ Recent content in ONLYOFFICE on PhllapsNET Hugo en-gb Thu, 08 Oct 2026 00:00:00 +0000 https://www.phllaps.net/posts/onlyoffice-docs-server-path-traversal-vulnerability/ Thu, 08 Oct 2026 00:00:00 +0000 https://www.phllaps.net/posts/onlyoffice-docs-server-path-traversal-vulnerability/ <div style="background:#b91c1c;color:white;padding:16px 18px;border-radius:14px;font-weight:800;font-size:18px;display:flex;align-items:center;gap:12px;box-shadow:0 10px 24px rgba(0,0,0,0.18);"><span style="font-size:24px;">🚨</span><span>SEVERITY: CRITICAL — CVSS 9.8</span><span style="opacity:0.95;font-weight:700;margin-left:auto;">Security Advisory</span></div> <h2 id="tldr-">TL;DR 📌</h2> <ul> <li>ONLYOFFICE Docs contains a path traversal vulnerability that can occur when JWT is used, via a /.. sequence in an image upload parameter and could allow for remote code execution.</li> <li>Highest CVSS: <strong>9.8 (Critical)</strong>.</li> <li><strong>Listed in CISA KEV</strong> (2026-10-08) — this is being exploited in the wild.</li> <li><strong>Fixed in <code>5.6.3</code></strong> — upgrade to this release or later.</li> <li>CVEs: CVE-2021-3199.</li> </ul> <h2 id="what-it-is">What it is</h2> <p>CVE-2021-3199 is a directory traversal flaw in ONLYOFFICE Document Server, reachable through the <code>/upload</code> endpoint. It affects deployments before version 5.6.3, specifically when JWT authentication is in use.</p>