CVE-2026-110725 — Fastify
LOWCVE-2026-110725 is a low-severity (CVSS 3.7) CWE-41 vulnerability. No vendor fix is recorded yet; mitigation options are listed below.
fast-uri is a dependency-free RFC 3986 URI parser and serializer for Node.js. In versions before 2.4.8, from 3.0.0 through 3.1.8, and from 4.0.0 through 4.2.2, when serialize(), normalize(),…
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-110725 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Description
fast-uri is a dependency-free RFC 3986 URI parser and serializer for Node.js. In versions before 2.4.8, from 3.0.0 through 3.1.8, and from 4.0.0 through 4.2.2, when serialize(), normalize(), or resolve() are called with the non-default option reference set to suffix on a reference that has no authority, the emitted relative reference can contain a bare colon in its first path segment without escaping it, even though RFC 3986 forbids that because it makes the string reparse as an absolute URI with a scheme. An application that serializes or normalizes a relative reference with the suffix option and then treats the result as a URI can turn inert input into a live javascript, data, or vbscript URL, a cross-site scripting vector, and the equal() comparison can conflate a scheme-bearing reference with a relative one. Exposure is limited to applications using the non-default suffix reference option. The issue is fixed in fast-uri 2.4.8, 3.1.9, and 4.2.3, and users should upgrade to one of these versions or later. As a workaround, avoid the suffix reference option on untrusted input, or percent-encode a colon in the first path segment of the result before treating it as a URI.
Detection & mitigation playbook
VulnerabilityDetect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Remediation status
No fixed release is recorded for CVE-2026-110725 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.
Mitigate without a patch
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This vulnerability is rated as having a Low impact because exploitation is constrained to applications invoking specific non-default parsing configurations on untrusted input without scheme authority. Across Red Hat products, this library is primarily embedded as an internal dependency within build pipelines and…
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.Source: Red Hat security advisory for CVE-2026-110725 (CC BY 4.0)
Frequently Asked Questions
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