{"answers":{"affected":"2 open source packages ship an affected version, including mcp.","exploited":"It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-67431 exists.","fix":"Upgrade mcp to 0.23.0 or later.","what":"CVE-2026-67431 is a high-severity missing authorization vulnerability in modelcontextprotocol ruby-sdk, published on 29 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-67431 and fix it if it is affected.\n\nWhat it is: CVE-2026-67431 is a high-severity missing authorization vulnerability in modelcontextprotocol ruby-sdk, published on 29 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-67431 exists.\n\nAffected packages and fixed versions:\n- mcp (RubyGems): affected all versions; fixed in 0.23.0\n- mcp (RubyGems): affected all versions; fixed in 0.23.0\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-67431/ (Markdown: https://insights.sbomify.com/CVE-2026-67431/index.md)","id":"CVE-2026-67431","markdown":"https://insights.sbomify.com/CVE-2026-67431/index.md","name":"CVE-2026-67431","record":{"aliases":["GHSA-5p9g-j988-pcwv"],"analysis":{"component_type":"library","fix_type":"upgrade","impacts":["code_execution","privilege_escalation"],"network_reachable":"yes","non_default_config":false,"product_category":"Ruby MCP SDK","requires_auth":"none","summary":"Attackers with stolen session IDs can execute tools in victim sessions due to missing session ownership binding in the Ruby MCP SDK.","user_interaction":"not_required","vuln_class":"missing_authorization"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"GitHub_M","cpe":[],"cvss":{"score":8.3,"severity":"high","source":"cna","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N","version":"4.0"},"cwes":[{"id":"CWE-284","name":"Improper Access Control"}],"description":"MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StreamableHTTPTransport in the mcp gem does not bind a session ID to a session owner, allowing an attacker with a stolen session ID to send tools/call requests that execute in the victim's session. This issue is fixed in version 0.23.0.","ecosystems":["RubyGems"],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"weaponised"},"has_fix":true,"headline":"MCP Ruby SDK: Ruby SSE Session Poisoning","id":"CVE-2026-67431","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"RubyGems","product":null,"products":[],"type":"missing_authorization","year":"2026"},"n_packages":2,"n_references":3,"next":{"headline":"MCP Ruby SDK: Unbounded JSON-RPC request body causes uncontrolled memory allocation in StreamableHTTPTransport","id":"CVE-2026-67432"},"packages":[{"ecosystem":"RubyGems","fixed":["0.23.0"],"introduced":["0"],"last_affected":[],"package":"mcp","purl":null,"source":"GHSA-5p9g-j988-pcwv"},{"ecosystem":"RubyGems","fixed":["0.23.0"],"introduced":["0"],"last_affected":[],"package":"mcp","purl":"pkg:gem/mcp","source":"GHSA-5p9g-j988-pcwv"}],"prev":{"headline":"MCP Ruby SDK: Unbounded session retention in StreamableHTTPTransport allows memory exhaustion via initialize flood","id":"CVE-2026-67430"},"products":["ruby-sdk"],"published":"2026-07-29","related":[],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"CC BY 4.0","name":"GitHub Advisory Database","prefix":"GHSA"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"yes","exploitation":"poc","technical_impact":"total"},"state":"PUBLISHED","updated":"2026-07-30","vendors":["modelcontextprotocol"]},"summary":"Attackers with stolen session IDs can execute tools in victim sessions due to missing session ownership binding in the Ruby MCP SDK.","url":"https://insights.sbomify.com/CVE-2026-67431/"}