{"id":"CVE-2026-55557","summary":"browse-mcp: Arbitrary file write via unconfined download and state paths","details":"browse-mcp is a Playwright-based headless-browser MCP server for MCP-capable agents. Prior to 0.8.2, browser_download writes a fetched response body to join(save_dir, filename) without validating the caller-controlled save_dir, while browser_save_state and browser_load_state honor a caller-controlled path unchanged. A malicious MCP client, or an autonomous agent steered by indirect prompt injection on a visited page, can choose an arbitrary save_dir or state path and a URL whose response body becomes attacker-controlled file contents, allowing writes to any path the process can reach, including ~/.bashrc, autostart entries, or cron files, and potentially leading to host code execution. The force_fetch fallback also uses a raw fetch() that bypasses the BROWSE_MCP_ALLOWED_ORIGINS origin fence. This issue is fixed in version 0.8.2.","aliases":["GHSA-m9mq-7m7q-xc6p"],"modified":"2026-08-27T11:47:40.307719092Z","published":"2026-08-25T16:28:07.368Z","database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-22"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55557.json"},"references":[{"type":"WEB","url":"https://github.com/That1Drifter/browse-mcp/blob/v0.8.2/CHANGELOG.md#082---2026-06-13"},{"type":"WEB","url":"https://github.com/That1Drifter/browse-mcp/releases/tag/v0.8.2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55557.json"},{"type":"ADVISORY","url":"https://github.com/That1Drifter/browse-mcp/security/advisories/GHSA-m9mq-7m7q-xc6p"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55557"},{"type":"FIX","url":"https://github.com/That1Drifter/browse-mcp/commit/5352a4a56f626254b445bfa07e4bb48c5aad15c1"},{"type":"FIX","url":"https://github.com/That1Drifter/browse-mcp/pull/58"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/that1drifter/browse-mcp","events":[{"introduced":"0"},{"fixed":"5352a4a56f626254b445bfa07e4bb48c5aad15c1"},{"fixed":"46d75f467d1a8f3c88b7224eacfd4038a969e7e8"}],"database_specific":{"source":["AFFECTED_FIELD","REFERENCES"],"extracted_events":[{"introduced":"0"},{"fixed":"0.8.2"}]}}],"versions":["v0.8.1","v0.8.0","v0.7.0","v0.6.0","v0.5.0","v0.4.1","v0.4.0","v0.3.0","v0.2.1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55557.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"}]}