{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "2.1.0"
              },
              {
                "fixed": "3.1.0"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "c45b7a361e56e6c753cd1c9b8cc4e1017090ce9c"
            },
            {
              "fixed": "8c6104c5d5daf41f0d454acc04d42dffa0e0d996"
            }
          ],
          "repo": "https://github.com/ether/etherpad",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-fjgc-3mj7-8rg8"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-444",
      "CWE-601",
      "CWE-79"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55087.json"
  },
  "details": "Etherpad is a real-time collaborative editor. From 2.1.0 until 3.1.0, Etherpad uses the attacker-controlled x-proxy-path request header in src/node/hooks/express/admin.ts when substituting paths into HTML, JavaScript, and CSS under /admin without sanitization, Vary: x-proxy-path, or Cache-Control: private, no-store. A shared proxy or CDN can cache the resulting response and serve attacker-injected script to an administrator. In src/node/hooks/express/specialpages.ts, version 3.0.0 also accepts a protocol-relative x-proxy-path value when constructing the /p/:pad/timeslider redirect, allowing redirection to an attacker-controlled host. The issues are exploitable when the deployment permits client-supplied x-proxy-path headers to reach Etherpad. This issue is fixed in version 3.1.0.",
  "id": "CVE-2026-55087",
  "modified": "2026-08-21T03:30:27.849700710Z",
  "published": "2026-08-19T19:29:16.221Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ether/etherpad/tree/3.1.0"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55087.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/ether/etherpad/security/advisories/GHSA-fjgc-3mj7-8rg8"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55087"
    },
    {
      "type": "FIX",
      "url": "https://github.com/ether/etherpad/commit/8c6104c5d5daf41f0d454acc04d42dffa0e0d996"
    },
    {
      "type": "FIX",
      "url": "https://github.com/ether/etherpad/pull/7784"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Etherpad: x-proxy-path header reflected into admin HTML/JS/CSS (cache-poisoning XSS) and concatenated into redirect (open-redirect)"
}