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Response snapshot Nov 2, 2026, 12:31 UTC

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VulnerabilityCVE-2026-117518

@fastify/reply-from is a Fastify plugin that forwards requests to an upstream HTTP server.

@fastify/reply-from is a Fastify plugin that forwards requests to an upstream HTTP server. In versions up to and including 12.8.

At a glance

Exploited
Not known
Severity
8.2 High (CVSS 3.1)
Chance of exploitation
Not estimated
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2026-117518 (opens a new tab)

What happened

@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.

Scores and how they were measured

CVSS base severity

8.2

Version 3.1As of

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

Not available

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Sources

  1. Primary source

    NVD CVE-2026-117518 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  2. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  3. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  4. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, November 2). @fastify/reply-from is a Fastify plugin that forwards requests to an upstream HTTP server. (CVE-2026-117518). https://kevwire.com/record/CVE-2026-117518

MLA

"@fastify/reply-from is a Fastify plugin that forwards requests to an upstream HTTP server. (CVE-2026-117518)." KEVWire, 2 Nov. 2026, kevwire.com/record/CVE-2026-117518.

Chicago

KEVWire. "@fastify/reply-from is a Fastify plugin that forwards requests to an upstream HTTP server. (CVE-2026-117518)." Last modified November 2, 2026. https://kevwire.com/record/CVE-2026-117518.

Evidence summary (plain text)

@fastify/reply-from is a Fastify plugin that forwards requests to an upstream HTTP server. (Nov 2, 2026).
@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.
CVSS 8.2 (version 3.1; evidence as of Nov 2, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-117518).
Sources:
NVD CVE-2026-117518: https://nvd.nist.gov/vuln/detail/CVE-2026-117518
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-11-02T10:55:57.149Z&lastModEndDate=2026-11-02T12:30:57.130Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-11-02T10:20:57.768Z&lastModEndDate=2026-11-02T11:55:55.935Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-11-02T09:45:58.882Z&lastModEndDate=2026-11-02T11:20:55.391Z&resultsPerPage=500&startIndex=0
Record ID: CVE-2026-117518.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Nov 2, 2026, 12:30 UTC. Ingestion is not an independent editorial investigation.

NVD status: Deferred. Publication in the NVD is not evidence of exploitation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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Record details

Record detail