{"cve":"CVE-2026-52830","nvd":{"published":"2026-07-02T21:16:56.847","modified":"2026-10-25T21:10:00.770","status":"Deferred","description":"fast-mcp-telegram is a Telegram MCP Server. Prior to 0.19.1, fast-mcp-telegram validates HTTP Bearer tokens by joining the raw token string into a session-file path. The verifier rejects the exact reserved token telegram, but it does not reject path separators or normalize the path before checking whether the session file exists. A remote HTTP client can therefore authenticate as the default legacy session with a token such as ../fast-mcp-telegram/telegram when the documented default session file ~/.config/fast-mcp-telegram/telegram.session exists. This bypasses the reserved session name control that is intended to prevent HTTP multi-user sessions from colliding with the default stdio or legacy account. With account-prefixed MCP tools enabled, the attacker still sees and calls the prefixed tools for the default account, so the prefix middleware does not stop the session selection bypass. This vulnerability is fixed in 0.19.1.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L","score":9.4},"cwes":["CWE-22","CWE-287"],"references":["https://github.com/advisories/GHSA-rxw2-pc8j-vxwm","https://web.archive.org/web/20250926152207/https://github.com/leshchenko1979/fast-mcp-telegram","https://github.com/advisories/GHSA-rxw2-pc8j-vxwm"],"products":[],"source":"nvd","synced_at":"2026-10-25T23:44:34.550481224+00:00"},"epss":{"cve":"CVE-2026-52830","score":0.00648,"percentile":0.50753,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-rxw2-pc8j-vxwm","url":"https://osv.dev/vulnerability/GHSA-rxw2-pc8j-vxwm","summary":"fast-mcp-telegram: Bearer token path traversal bypasses reserved Telegram session protection","modified":"2026-08-13T17:00:11.550815092Z","packages":[{"ecosystem":"PyPI","name":"fast-mcp-telegram","purl":"pkg:pypi/fast-mcp-telegram","ranges":["<0.19.1"],"fixed":["0.19.1"]}]},{"id":"PYSEC-2026-2473","url":"https://osv.dev/vulnerability/PYSEC-2026-2473","summary":"fast-mcp-telegram: Bearer token path traversal bypasses reserved Telegram session protection","modified":"2026-07-13T16:31:55.165460679Z","packages":[{"ecosystem":"PyPI","name":"fast-mcp-telegram","purl":"pkg:pypi/fast-mcp-telegram","ranges":["<0.19.1"],"fixed":["0.19.1"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}