CVE-2020-26291: URI.js is a javascript URL mutation library (npm package urijs). In URI.js before version 1.19.4, the hostname can be spoofed by using a backslash (`\...

Description

URI.js is a javascript URL mutation library (npm package urijs). In URI.js before version 1.19.4, the hostname can be spoofed by using a backslash (`\`) character followed by an at (`@`) character. If the hostname is used in security decisions, the decision may be incorrect. Depending on library usage and attacker intent, impacts may include allow/block list bypasses, SSRF attacks, open redirects, or other undesired behavior. For example the URL `https://expected-example.com\@observed-example.com` will incorrectly return `observed-example.com` if using an affected version. Patched versions correctly return `expected-example.com`. Patched versions match the behavior of other parsers which implement the WHATWG URL specification, including web browsers and Node's built-in URL class. Version 1.19.4 is patched against all known payload variants. Version 1.19.3 has a partial patch but is still vulnerable to a payload variant.]

Metrics

CVSS 3.1

6.5/10

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

EPSS Probability

1.69%

74.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-20

Affected Software

Vendor	Product	Versions
Uri.Js Project	Uri.Js	< 1.19.4

References

https://github.com/medialize/URI.js/commit/b02bf037c99ac9316b77ff8bfd840e90becf1155Patch, Third Party Advisory
https://github.com/medialize/URI.js/releases/tag/v1.19.4Release Notes, Third Party Advisory
https://github.com/medialize/URI.js/security/advisories/GHSA-3329-pjwv-fjpgThird Party Advisory
https://www.npmjs.com/package/urijsThird Party Advisory
https://github.com/medialize/URI.js/commit/b02bf037c99ac9316b77ff8bfd840e90becf1155Patch, Third Party Advisory
https://github.com/medialize/URI.js/releases/tag/v1.19.4Release Notes, Third Party Advisory
https://github.com/medialize/URI.js/security/advisories/GHSA-3329-pjwv-fjpgThird Party Advisory
https://www.npmjs.com/package/urijsThird Party Advisory

Timeline

Published: Dec 31, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-26291?

URI.js is a javascript URL mutation library (npm package urijs). In URI.js before version 1.19.4, the hostname can be spoofed by using a backslash (`\`) character followed by an at (`@`) character. If the hostname is used in security decisions, the decision may be incorrect. Depending on library usage and attacker intent, impacts may include allow/block list bypasses, SSRF attacks, open redirects, or other undesired behavior. For example the URL `https://expected-example.com\@observed-example.com` will incorrectly return `observed-example.com` if using an affected version. Patched versions correctly return `expected-example.com`. Patched versions match the behavior of other parsers which implement the WHATWG URL specification, including web browsers and Node's built-in URL class. Version 1.19.4 is patched against all known payload variants. Version 1.19.3 has a partial patch but is still vulnerable to a payload variant.]

How severe is CVE-2020-26291?

CVE-2020-26291 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 1.69% probability of exploitation in the next 30 days.

How do I fix CVE-2020-26291?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.