{"schemaVersion":3,"id":"CVE-2026-52869","aliases":["GHSA-jpw9-pfvf-9f58","PYSEC-2026-3482","CGA-5grw-wmrx-hp7r","CGA-fqjr-h24p-rmpg","CGA-5jqw-mh4q-9pxj","CGA-8w96-2jv2-wwvx","CGA-r36x-q685-vj43"],"status":"published","duplicateOf":null,"title":null,"description":"The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to 1.27.2, the SSE and stateful Streamable HTTP transports mcp.server.sse.SseServerTransport and mcp.server.streamable_http_manager.StreamableHTTPSessionManager route requests to existing sessions using only the session_id query parameter or Mcp-Session-Id header without verifying the authenticated principal that created the session, allowing a different bearer-token-authenticated client with a known session ID to inject JSON-RPC messages into that session. This issue is fixed in version 1.27.2.","dates":{"published":"2026-07-15T20:06:23.604Z","modified":"2026-07-16T13:00:37.854Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":7.1,"severity":"high","version":"3.1","versionLabel":"v3.1","source":"CVE.org","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","score":7.1,"severity":"high","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Pypi","score":7.1,"severity":"high","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L","exploitability":4.1,"impact":9.2,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Wolfi","score":7.1,"severity":"high","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L","exploitability":4.1,"impact":9.2,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Chainguard","score":7.1,"severity":"high","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L","exploitability":4.1,"impact":9.2,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":7.1,"severity":"high","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.00535,"percentile":0.44021,"severity":"low","asOf":"2026-10-20T00:00:00.000Z","change":{"pp":0,"baselineDate":"2026-09-20T00:00:00.000Z","baselineScore":0.00535},"history":[{"date":"2026-09-14T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-15T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-16T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-17T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-18T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-19T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00535,"percentile":0.44021}],"last30":[{"date":"2026-09-20T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00535,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00535,"percentile":0.44021}]},"kev":{"state":"not-listed","entries":[],"listedCount":0,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":false,"entry":null},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"none-recorded","sources":[]},"exploits":[],"exploitCount":0,"weaknesses":[{"id":"CWE-639","name":"Authorization Bypass Through User-Controlled Key","description":"The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.","type":"weakness","status":"Incomplete","abstraction":"Base","likelihoodOfExploit":"High","url":"https://cwe.mitre.org/data/definitions/639.html"}],"affected":[{"vendor":"chainguard","product":"kserve-huggingfaceserver-cuda-13.3","name":"kserve-huggingfaceserver-cuda-13.3","label":"kserve-huggingfaceserver-cuda-13.3","ecosystem":"Chainguard","cpePart":null,"purl":"pkg:apk/chainguard/kserve-huggingfaceserver-cuda-13.3","purlType":"apk","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null},{"text":"< 0.21.0-r4","noFixRecorded":false,"fixedIn":null}],"versionsText":"All versions (No fix recorded) | < 0.21.0-r4","eol":null,"hubHref":null},{"vendor":"chainguard","product":"litellm","name":"litellm","label":"litellm","ecosystem":"Chainguard","cpePart":null,"purl":"pkg:apk/chainguard/litellm","purlType":"apk","versions":[{"text":"< 1.91.2-r2","noFixRecorded":false,"fixedIn":null},{"text":"< 1.93.0-r0","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 1.91.2-r2 | < 1.93.0-r0","eol":null,"hubHref":null},{"vendor":"chainguard","product":"semgrep","name":"semgrep","label":"semgrep","ecosystem":"Chainguard","cpePart":null,"purl":"pkg:apk/chainguard/semgrep","purlType":"apk","versions":[{"text":"< 1.172.0-r1","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 1.172.0-r1","eol":null,"hubHref":null},{"vendor":"wolfi","product":"semgrep","name":"semgrep","label":"semgrep","ecosystem":"Wolfi","cpePart":null,"purl":"pkg:apk/wolfi/semgrep","purlType":"apk","versions":[{"text":"< 1.172.0-r1","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 1.172.0-r1","eol":null,"hubHref":null},{"vendor":"lfprojects","product":"mcp_python_sdk","name":"mcp python sdk","label":"mcp_python_sdk","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"< 1.27.2","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 1.27.2","eol":null,"hubHref":"/vendor/lfprojects/mcp_python_sdk"},{"vendor":"modelcontextprotocol","product":"python-sdk","name":"python-sdk","label":"python-sdk","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"< 1.27.2","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 1.27.2","eol":null,"hubHref":"/vendor/modelcontextprotocol/python-sdk"},{"vendor":"PyPI","product":"mcp","name":"mcp","label":"mcp","ecosystem":"PyPI","cpePart":null,"purl":"pkg:pypi/mcp","purlType":"pypi","versions":[{"text":"< 1.27.2","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 1.27.2","eol":null,"hubHref":null}],"affectedCount":7,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-jpw9-pfvf-9f58","label":"github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-jpw9-pfvf-9f58","hostname":"github.com","tags":["X Refsource CONFIRM","WEB","Advisory","Vendor Advisory"]},{"url":"https://github.com/modelcontextprotocol/python-sdk/pull/2690","label":"github.com/modelcontextprotocol/python-sdk/pull/2690","hostname":"github.com","tags":["X Refsource MISC","WEB","FIX","Issue Tracking","Patch"]},{"url":"https://github.com/modelcontextprotocol/python-sdk/pull/2719","label":"github.com/modelcontextprotocol/python-sdk/pull/2719","hostname":"github.com","tags":["X Refsource MISC","WEB","FIX","Issue Tracking","Patch"]},{"url":"https://github.com/modelcontextprotocol/python-sdk/commit/1abcca2408a6b50e10ec601181f63f9978705c00","label":"github.com/modelcontextprotocol/python-sdk/commit/1abcca2408a6b50e10ec601181f63f9978705c00","hostname":"github.com","tags":["X Refsource MISC","WEB","FIX","Patch"]},{"url":"https://github.com/modelcontextprotocol/python-sdk/commit/ce267b6fc515dc4efc1dc70b6975b16ff0feef0a","label":"github.com/modelcontextprotocol/python-sdk/commit/ce267b6fc515dc4efc1dc70b6975b16ff0feef0a","hostname":"github.com","tags":["X Refsource MISC","WEB","FIX","Patch"]},{"url":"https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2","label":"github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2","hostname":"github.com","tags":["X Refsource MISC","WEB","Release Notes"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-52869","label":"nvd.nist.gov/vuln/detail/CVE-2026-52869","hostname":"nvd.nist.gov","tags":["Advisory"]},{"url":"https://github.com/modelcontextprotocol/python-sdk","label":"github.com/modelcontextprotocol/python-sdk","hostname":"github.com","tags":["PACKAGE"]},{"url":"https://pypi.org/project/mcp","label":"pypi.org/project/mcp","hostname":"pypi.org","tags":["PACKAGE"]},{"url":"https://github.com/advisories/GHSA-jpw9-pfvf-9f58","label":"github.com/advisories/GHSA-jpw9-pfvf-9f58","hostname":"github.com","tags":["Advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52869.json","label":"github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52869.json","hostname":"github.com","tags":["Advisory"]}],"lineage":{"upstream":[],"downstream":[],"duplicates":[],"related":["CGA-RMX9-94G8-226F"]},"timeline":[{"kind":"published","date":"2026-07-15T20:06:23.604Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2026-07-16T13:00:37.854Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":29,"level":"medium","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-21T06:48:11.186Z","stale":false,"partial":false}}