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URIjs Hostname spoofing via backslashes in URL

High severity GitHub Reviewed Published Feb 22, 2021 in medialize/URI.js • Updated Dec 8, 2023

Package

npm urijs (npm)

Affected versions

< 1.19.6

Patched versions

1.19.6

Description

Impact

If using affected versions to determine a URL's hostname, the hostname can be spoofed by using a backslash (\) character as part of the scheme delimiter, e.g. scheme:/\hostname. 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.

Example URL: https:/\expected-example.com/path
Escaped string: https:/\\expected-example.com/path (JavaScript strings must escape backslash)

Affected versions incorrectly return no hostname. 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.

Patches

Version 1.19.6 is patched against all known payload variants.

References

https://github.com/medialize/URI.js/releases/tag/v1.19.6 (fix for this particular bypass)
https://github.com/medialize/URI.js/releases/tag/v1.19.4 (fix for related bypass)
https://github.com/medialize/URI.js/releases/tag/v1.19.3 (fix for related bypass)
PR #233 (initial fix for backslash handling)

For more information

If you have any questions or comments about this advisory, open an issue in https://github.com/medialize/URI.js

Reporter credit

Yaniv Nizry from the CxSCA AppSec team at Checkmarx

References

Published by the National Vulnerability Database Feb 22, 2021
@rodneyrehm rodneyrehm published to medialize/URI.js Feb 22, 2021
Reviewed Feb 26, 2021
Published to the GitHub Advisory Database Mar 1, 2021
Last updated Dec 8, 2023

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS score

0.276%
(69th percentile)

Weaknesses

CVE ID

CVE-2021-27516

GHSA ID

GHSA-p6j9-7xhc-rhwp

Source code

Credits

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