{"url":"http://public2.vulnerablecode.io/api/packages/991275?format=json","purl":"pkg:npm/mcp-handler@0.0.0-7a941a0f-20260220182431","type":"npm","namespace":"","name":"mcp-handler","version":"0.0.0-7a941a0f-20260220182431","qualifiers":{},"subpath":"","is_vulnerable":true,"next_non_vulnerable_version":"1.1.0","latest_non_vulnerable_version":"1.1.0","affected_by_vulnerabilities":[{"url":"http://public2.vulnerablecode.io/api/vulnerabilities/359896?format=json","vulnerability_id":"VCID-2vy1-3cyp-x7g5","summary":"mcp-handler has a tool response leak across concurrent client sessions ('Race Condition')\n`mcp-handler` versions prior to 1.1.0 accepted `@modelcontextprotocol/sdk` < 1.26.0 as a peer dependency. That SDK version contains a vulnerability [[CVE-2026-25536](https://nvd.nist.gov/vuln/detail/CVE-2026-25536)] that causes concurrent requests from different clients to share server-side state including authentication context and tool execution results when a `StreamableHTTPServerTransport` instance is reused across requests.\n\n**Note:** This is _not_ a vulnerability in `mcp-handler` itself. The root cause is in the peer dependency `@modelcontextprotocol/sdk`. \n\n### Impact\n\nA low-privileged attacker making concurrent requests to an `mcp-handler` endpoint can read another client's session data, including authentication information and tool execution state. This is a confidentiality breach with potential for limited integrity impact.\n\n**Root Cause:** [CVE-2026-25536](https://nvd.nist.gov/vuln/detail/CVE-2026-25536) in `@modelcontextprotocol/sdk` < 1.26.0. The SDK did not prevent reuse of stateless transports across client connections.\n\n### Patches\n\nUpgrade to `mcp-handler@1.1.0`. This release raises the minimum peer dependency to `@modelcontextprotocol/sdk@>=1.26.0`, which contains the fix for CVE-2026-25536. \n\n### Workarounds\n\n- Upgrade `@modelcontextprotocol/sdk` to `>=1.26.0` (note: the SDK will throw on transport reuse, which will break `mcp-handler` < 1.1.0 which effectively forces the upgrade)\n- Alternatively, manually create fresh `McpServer` and transport instances per request in your handler code","references":[{"reference_url":"https://github.com/vercel/mcp-handler","reference_id":"","reference_type":"","scores":[{"value":"7.1","scoring_system":"cvssv3.1","scoring_elements":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N"},{"value":"HIGH","scoring_system":"generic_textual","scoring_elements":""}],"url":"https://github.com/vercel/mcp-handler"},{"reference_url":"https://github.com/vercel/mcp-handler/security/advisories/GHSA-w2fm-25vw-vh7f","reference_id":"","reference_type":"","scores":[{"value":"7.1","scoring_system":"cvssv3.1","scoring_elements":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N"},{"value":"HIGH","scoring_system":"cvssv3.1_qr","scoring_elements":""},{"value":"HIGH","scoring_system":"generic_textual","scoring_elements":""}],"url":"https://github.com/vercel/mcp-handler/security/advisories/GHSA-w2fm-25vw-vh7f"},{"reference_url":"https://nvd.nist.gov/vuln/detail/CVE-2026-25536","reference_id":"CVE-2026-25536","reference_type":"","scores":[{"value":"7.1","scoring_system":"cvssv3.1","scoring_elements":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N"},{"value":"HIGH","scoring_system":"generic_textual","scoring_elements":""}],"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-25536"},{"reference_url":"https://github.com/advisories/GHSA-345p-7cg4-v4c7","reference_id":"GHSA-345p-7cg4-v4c7","reference_type":"","scores":[{"value":"7.1","scoring_system":"cvssv3.1","scoring_elements":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N"},{"value":"HIGH","scoring_system":"generic_textual","scoring_elements":""}],"url":"https://github.com/advisories/GHSA-345p-7cg4-v4c7"},{"reference_url":"https://github.com/advisories/GHSA-w2fm-25vw-vh7f","reference_id":"GHSA-w2fm-25vw-vh7f","reference_type":"","scores":[{"value":"HIGH","scoring_system":"cvssv3.1_qr","scoring_elements":""}],"url":"https://github.com/advisories/GHSA-w2fm-25vw-vh7f"}],"fixed_packages":[{"url":"http://public2.vulnerablecode.io/api/packages/374061?format=json","purl":"pkg:npm/mcp-handler@1.1.0","is_vulnerable":false,"affected_by_vulnerabilities":[],"resource_url":"http://public2.vulnerablecode.io/packages/pkg:npm/mcp-handler@1.1.0"}],"aliases":["GHSA-w2fm-25vw-vh7f"],"risk_score":null,"exploitability":null,"weighted_severity":null,"resource_url":"http://public2.vulnerablecode.io/vulnerabilities/VCID-2vy1-3cyp-x7g5"}],"fixing_vulnerabilities":[],"risk_score":null,"resource_url":"http://public2.vulnerablecode.io/packages/pkg:npm/mcp-handler@0.0.0-7a941a0f-20260220182431"}