{"answers":{"affected":"2 open source packages ship an affected version, including auth-fetch-mcp.","exploited":"There is no known exploitation of CVE-2026-49857 in the wild and no public exploit code.","fix":"Upgrade auth-fetch-mcp to 3.0.2 or later.","what":"CVE-2026-49857 is a high-severity server-side request forgery vulnerability in ymw0407 auth-fetch-mcp, published on 13 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link."},"fix_prompt":"Check this codebase for CVE-2026-49857 and fix it if it is affected.\n\nWhat it is: CVE-2026-49857 is a high-severity server-side request forgery vulnerability in ymw0407 auth-fetch-mcp, published on 13 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.\nExploitation: There is no known exploitation of CVE-2026-49857 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- auth-fetch-mcp (npm): affected all versions; fixed in 3.0.2\n- auth-fetch-mcp (npm): affected all versions; fixed in 3.0.2\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-2026-49857/ (Markdown: https://insights.sbomify.com/CVE-2026-49857/index.md)","id":"CVE-2026-49857","markdown":"https://insights.sbomify.com/CVE-2026-49857/index.md","name":"CVE-2026-49857","record":{"aliases":["GHSA-pvrj-8cg3-j5f8"],"analysis":{"component_type":"library","fix_type":"upgrade","impacts":["data_read","security_bypass"],"network_reachable":"yes","non_default_config":false,"product_category":"MCP server library","requires_auth":"none","summary":"An SSRF protection bypass in auth-fetch-mcp allows attackers to access loopback services via IPv4-mapped IPv6 addresses, exposing internal data.","user_interaction":"required","vuln_class":"ssrf"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"GitHub_M","cpe":[],"cvss":{"score":7.4,"severity":"high","source":"cna","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N","version":"3.1"},"cwes":[{"id":"CWE-918","name":"Server-Side Request Forgery"}],"description":"auth-fetch-mcp is an MCP server that lets AI assistants fetch content from authenticated web pages. Version 3.0.1 implements SSRF protection in `assertSafeUrl()` (`src/security.ts`) to block requests to private and loopback addresses. However, the `isPrivateV6()` function fails to detect IPv4-mapped IPv6 loopback addresses in their hex-normalized form. When an attacker supplies a URL such as `http://[::ffff:127.0.0.1]:PORT/`, the Node.js WHATWG URL parser silently normalizes the host to `[::ffff:7f00:1]`. Because `net.isIPv4('7f00:1')` returns `false`, the private-IP check is bypassed and the URL is passed to the browser or HTTP client, allowing the MCP tool to reach loopback services that are supposed to be blocked. The issue is exploitable under default configuration without any special environment variable. Version 3.0.1 patches the issue.","ecosystems":["npm"],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"auth-fetch-mcp has SSRF Protection Bypass via IPv4-mapped IPv6 Loopback","id":"CVE-2026-49857","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"npm","product":null,"products":[],"type":"ssrf","year":"2026"},"n_packages":2,"n_references":3,"next":{"headline":"API Platform Core: Cross-user attribute leak in JSON:API and HAL item normalizers due to missing isCacheKeySafe gate","id":"CVE-2026-49858"},"packages":[{"ecosystem":"npm","fixed":["3.0.2"],"introduced":["0"],"last_affected":[],"package":"auth-fetch-mcp","purl":null,"source":"GHSA-pvrj-8cg3-j5f8"},{"ecosystem":"npm","fixed":["3.0.2"],"introduced":["0"],"last_affected":[],"package":"auth-fetch-mcp","purl":"pkg:npm/auth-fetch-mcp","source":"GHSA-pvrj-8cg3-j5f8"}],"prev":{"headline":"@jshookmcp/jshook: ICMP probe and traceroute skip local-network SSRF authorization","id":"CVE-2026-49856"},"products":["auth-fetch-mcp"],"published":"2026-08-13","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":"no","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-08-13","vendors":["ymw0407"]},"summary":"An SSRF protection bypass in auth-fetch-mcp allows attackers to access loopback services via IPv4-mapped IPv6 addresses, exposing internal data.","url":"https://insights.sbomify.com/CVE-2026-49857/"}