CVE-2026-117518

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{"bugzilla": {"description": "reply-from: reply-from: Unauthorized upstream access via path traversal", "id": "2565299", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2565299"}, "csaw": false, "cvss3": {"cvss3_base_score": "8.2", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N", "status": "draft"}, "cwe": "CWE-22", "details": ["@fastify/reply-from is a Fastify plugin that forwards requests to an upstream HTTP server. In versions up to and including 12.8.0, the plugin validated proxy paths against forward-slash dot-segments only and then built the target with the WHATWG URL parser, which normalizes a backslash and its percent-encoded form to a forward slash on the http, https, ws, and wss schemes. A path that uses backslash dot-segments therefore bypasses the traversal check and resolves to a different upstream path, so an application that scopes proxying to an upstream prefix, or relies on route guards in front of the forwarding call, can have an unauthenticated request escape the intended prefix and reach other upstream endpoints. The resulting access to unintended upstream resources is primarily a confidentiality impact with limited integrity impact. The issue is fixed in @fastify/reply-from 12.8.1, where the path is normalized and any segment resolving to a single or double dot, along with control characters and ambiguous whitespace, is rejected before the URL is constructed, and users should upgrade to 12.8.1 or later. There is no workaround other than upgrading.", "A flaw was found in @fastify/reply-from. The plugin only validates forward-slash dot-segments, allowing backslash sequences to bypass traversal checks when the upstream destination URL is constructed. An unauthenticated remote attacker can exploit this vulnerability by submitting requests with crafted path traversal sequences. This flaw allows an attacker to bypass intended proxy prefix restrictions and access unauthorized upstream endpoints, potentially leading to sensitive information disclosure."], "name": "CVE-2026-117518", "public_date": "2026-11-02T10:39:22Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-117518\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-117518\nhttps://cna.openjsf.org/security-advisories.html\nhttps://github.com/fastify/fastify-reply-from/security/advisories/GHSA-vp2r-3vgv-32g9"], "statement": "Red Hat has rated this vulnerability as having an Important security impact because an unauthenticated remote attacker can bypass routing restrictions without requiring privileges. In deployments where Fastify applications use the reply-from plugin as an edge gateway or reverse proxy boundary, circumventing path scoping permits requests to escape into unintended backend systems. This unauthorized reach poses a high confidentiality risk across internal networks, while overall integrity impact is limited to the functionality exposed by reachable upstream endpoints.", "threat_severity": "Important"}

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