{"answers":{"affected":"2 open source packages ship an affected version, including @modelcontextprotocol/sdk. It affects 1 product.","exploited":"It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-0621 exists.","fix":"Upgrade @modelcontextprotocol/sdk to 1.25.2 or later.","what":"CVE-2026-0621 is a high-severity denial of service vulnerability in Anthropic MCP TypeScript SDK, published on 5 Jan 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-2026-0621 and fix it if it is affected.\n\nWhat it is: CVE-2026-0621 is a high-severity denial of service vulnerability in Anthropic MCP TypeScript SDK, published on 5 Jan 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-2026-0621 exists.\n\nAffected packages and fixed versions:\n- @modelcontextprotocol/sdk (npm): affected from 1.3.0; fixed in 1.25.2\n- @modelcontextprotocol/sdk (npm): affected from 1.3.0; fixed in 1.25.2\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-2026-0621/ (Markdown: https://insights.sbomify.com/CVE-2026-0621/index.md)","id":"CVE-2026-0621","markdown":"https://insights.sbomify.com/CVE-2026-0621/index.md","name":"CVE-2026-0621","record":{"aliases":["CLSA-2026-1789750026","ECHO-6585-27e0-f504","GHSA-8r9q-7v3j-jr4g","MINI-38mh-cmqx-4f24","MINI-434q-rwv3-qx4x","MINI-c8pg-4wwg-537f","MINI-f29q-8gc2-j42v","MINI-q38r-8wg3-7449","ROOT-APP-NPM-CVE-2026-0621"],"analysis":{"component_type":"library","fix_type":"upgrade","impacts":["denial_of_service"],"network_reachable":"yes","non_default_config":false,"product_category":"MCP TypeScript SDK","requires_auth":"none","summary":"Attackers can cause denial of service in applications using the MCP TypeScript SDK by sending malicious URIs that trigger catastrophic backtracking in URI template processing.","user_interaction":"not_required","vuln_class":"denial_of_service"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"VulnCheck","cpe":[{"product":"mcp_typescript_sdk","vendor":"lfprojects"}],"cvss":{"score":8.7,"severity":"high","source":"cna","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","version":"4.0"},"cwes":[{"id":"CWE-1333","name":"Inefficient Regular Expression Complexity"}],"description":"Anthropic's MCP TypeScript SDK versions up to and including 1.25.1 contain a regular expression denial of service (ReDoS) vulnerability in the UriTemplate class when processing RFC 6570 exploded array patterns. The dynamically generated regular expression used during URI matching contains nested quantifiers that can trigger catastrophic backtracking on specially crafted inputs, resulting in excessive CPU consumption. An attacker can exploit this by supplying a malicious URI that causes the Node.js process to become unresponsive, leading to a denial of service.","ecosystems":["npm"],"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 TypeScript SDK UriTemplate Exploded Array Pattern ReDoS","id":"CVE-2026-0621","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"npm","product":null,"products":[],"type":"denial_of_service","year":"2026"},"n_packages":2,"n_references":2,"next":{"headline":"Open 5GS WebUI uses a hard-coded JWT signing key","id":"CVE-2026-0622"},"packages":[{"ecosystem":"npm","fixed":["1.25.2"],"introduced":["1.3.0"],"last_affected":[],"package":"@modelcontextprotocol/sdk","purl":null,"source":"GHSA-8r9q-7v3j-jr4g"},{"ecosystem":"npm","fixed":["1.25.2"],"introduced":["1.3.0"],"last_affected":[],"package":"@modelcontextprotocol/sdk","purl":"pkg:npm/%40modelcontextprotocol/sdk","source":"GHSA-8r9q-7v3j-jr4g"}],"prev":{"headline":"L2TP over IPSec Encryption Failure on ArcherAXE75","id":"CVE-2026-0620"},"products":["MCP TypeScript SDK"],"published":"2026-01-05","related":[{"cvss_score":7.6,"headline":"DNS Rebinding Protection Disabled by Default in Model Context Protocol TypeScript SDK for Servers Running on Localhost","id":"CVE-2025-66414","kev_date_added":null,"published":"2025-12-02"},{"cvss_score":7.1,"headline":"@modelcontextprotocol/sdk has cross-client data leak via shared server/transport instance reuse","id":"CVE-2026-25536","kev_date_added":null,"published":"2026-02-04"}],"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":"US public information, NVD API terms","name":"NVD"},{"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":"partial"},"state":"PUBLISHED","updated":"2026-10-08","vendors":["Anthropic"]},"summary":"Attackers can cause denial of service in applications using the MCP TypeScript SDK by sending malicious URIs that trigger catastrophic backtracking in URI template processing.","url":"https://insights.sbomify.com/CVE-2026-0621/"}