CVE-2026-110725

fast-uri vulnerable to scheme injection via an unescaped first-segment colon in suffix references

Workarounds

Do not use the reference: 'suffix' option on untrusted input. If suffix output is required, percent-encode a colon in the first path segment of the result before treating it as a URI.

fast-uri's serialize(), normalize(), and resolve(), when called with the non-default option reference: 'suffix' on a reference that has no authority, emit a relative reference whose first path segment contains a bare colon without escaping it. RFC 3986 section 3.3 requires the first segment of a path-noscheme reference not to contain a colon, precisely because a bare colon makes the string reparse as an absolute URI with a scheme. fast-uri's default serialization escapes that colon, but the suffix path does not.

For example, normalize('javascript:alert(1)', { reference: 'suffix' }) returns javascript:alert(1), which reparses as a live javascript: scheme; data: and vbscript: behave the same.

Applications that serialize or normalize a relative reference with reference: 'suffix' and then treat the result as a URI can turn inert input into a live javascript:, data:, or vbscript: URL (a cross-site scripting vector), and equal() can conflate a scheme-bearing reference with a relative one. Exposure is limited to applications that use the non-default reference: 'suffix' option.

CVE-2026-110725 has a CVSS score of 3.7 (Low). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.4.8, 3.1.9, 4.2.3); upgrading removes the vulnerable code path.

Kodem intelligence

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Upgrade to fast-uri 2.4.8, 3.1.9, or 4.2.3.

1. What is CVE-2026-110725? CVE-2026-110725 is a low-severity security vulnerability in fast-uri (npm), affecting versions < 2.4.8. It is fixed in 2.4.8, 3.1.9, 4.2.3.
2. How severe is CVE-2026-110725? CVE-2026-110725 has a CVSS score of 3.7 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of fast-uri are affected by CVE-2026-110725? fast-uri (npm) versions < 2.4.8 is affected.
4. Is there a fix for CVE-2026-110725? Yes. CVE-2026-110725 is fixed in 2.4.8, 3.1.9, 4.2.3. Upgrade to this version or later.
5. Is CVE-2026-110725 exploitable, and should I be worried? Whether CVE-2026-110725 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-110725 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-110725?
   • Upgrade fast-uri to 2.4.8 or later
   • Upgrade fast-uri to 3.1.9 or later
   • Upgrade fast-uri to 4.2.3 or later

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