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    2 vulnerabilities by @fastify/express

    CVE-2026-6556 (GCVE-0-2026-6556)

    Vulnerability from nvd – Published: 2026-06-30 12:48 – Updated: 2026-06-30 13:30
    VLAI
    Title
    @fastify/express vulnerable to middleware bypass via non-string mount paths in prefixed plugins
    Summary
    @fastify/express versions 4.0.6 and earlier only rewrite the plugin prefix for middleware mount paths when the path argument is a string. Non-string mount paths (arrays of paths and regular expressions) are left unprefixed inside prefixed plugin scopes, so middleware registered with those forms does not match the actual prefixed request path. Applications that use path-scoped middleware for authentication, authorization, rate limiting, or auditing on routes inside a prefixed scope can be bypassed by sending a request to the prefixed route, because Fastify still matches the route but the middleware is skipped. Patches: upgrade to @fastify/express 4.0.7. Workarounds: use string mount paths instead of arrays or regular expressions in prefixed plugins, or register one use call per path.
    Severity
    9.1 (Critical)
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
    SSVC
    Exploitation: none Automatable: yes Technical Impact: total
    CISA Coordinator (v2.0.3)
    CWE
    Assigner
    References
    Impacted products
    Vendor Product Version
    @fastify/express @fastify/express Affected: 0 , < 4.0.7 (semver)
    Unaffected: 4.0.7 (semver)
    		Create a notification for this product.
    Credits
    Jvr2022 UlisesGascon
    Show details on NVD website
    To clipboard 

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    CVE-2026-6556 (GCVE-0-2026-6556)

    Vulnerability from cvelistv5 – Published: 2026-06-30 12:48 – Updated: 2026-06-30 13:30
    VLAI
    Title
    @fastify/express vulnerable to middleware bypass via non-string mount paths in prefixed plugins
    Summary
    @fastify/express versions 4.0.6 and earlier only rewrite the plugin prefix for middleware mount paths when the path argument is a string. Non-string mount paths (arrays of paths and regular expressions) are left unprefixed inside prefixed plugin scopes, so middleware registered with those forms does not match the actual prefixed request path. Applications that use path-scoped middleware for authentication, authorization, rate limiting, or auditing on routes inside a prefixed scope can be bypassed by sending a request to the prefixed route, because Fastify still matches the route but the middleware is skipped. Patches: upgrade to @fastify/express 4.0.7. Workarounds: use string mount paths instead of arrays or regular expressions in prefixed plugins, or register one use call per path.
    Severity
    9.1 (Critical)
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
    SSVC
    Exploitation: none Automatable: yes Technical Impact: total
    CISA Coordinator (v2.0.3)
    CWE
    Assigner
    References
    Impacted products
    Vendor Product Version
    @fastify/express @fastify/express Affected: 0 , < 4.0.7 (semver)
    Unaffected: 4.0.7 (semver)
    		Create a notification for this product.
    Credits
    Jvr2022 UlisesGascon
    Show details on NVD website
    To clipboard 

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