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    2 vulnerabilities by ymw0407

    CVE-2026-49857 (GCVE-0-2026-49857)

    Vulnerability from nvd – Published: 2026-08-13 14:50 – Updated: 2026-08-13 17:52
    VLAI
    Title
    auth-fetch-mcp has SSRF Protection Bypass via IPv4-mapped IPv6 Loopback
    Summary
    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.
    Severity
    7.4 (High)
    CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N
    SSVC
    Exploitation: none Automatable: no Technical Impact: partial
    CISA Coordinator · CISA-ADP (v2.0.3)
    Decision recorded 2026-08-13 17:50 UTC
    CWE
    • CWE-918 - Server-Side Request Forgery (SSRF)
    Assigner
    References
    Impacted products
    Vendor Product Version
    ymw0407 auth-fetch-mcp Affected: < 3.0.2
    		Create a notification for this product.
    Show details on NVD website
    To clipboard 

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    CVE-2026-49857 (GCVE-0-2026-49857)

    Vulnerability from cvelistv5 – Published: 2026-08-13 14:50 – Updated: 2026-08-13 17:52
    VLAI
    Title
    auth-fetch-mcp has SSRF Protection Bypass via IPv4-mapped IPv6 Loopback
    Summary
    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.
    Severity
    7.4 (High)
    CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N
    SSVC
    Exploitation: none Automatable: no Technical Impact: partial
    CISA Coordinator · CISA-ADP (v2.0.3)
    Decision recorded 2026-08-13 17:50 UTC
    CWE
    • CWE-918 - Server-Side Request Forgery (SSRF)
    Assigner
    References
    Impacted products
    Vendor Product Version
    ymw0407 auth-fetch-mcp Affected: < 3.0.2
    		Create a notification for this product.
    Show details on NVD website
    To clipboard 

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