CVSS2
Attack Vector
NETWORK
Attack Complexity
LOW
Authentication
NONE
Confidentiality Impact
PARTIAL
Integrity Impact
NONE
Availability Impact
NONE
AV:N/AC:L/Au:N/C:P/I:N/A:N
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
NONE
Availability Impact
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS
Percentile
68.3%
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.
Version 1.19.6 is patched against all known payload variants.
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)
If you have any questions or comments about this advisory, open an issue in https://github.com/medialize/URI.js
Yaniv Nizry from the CxSCA AppSec team at Checkmarx
advisory.checkmarx.net/advisory/CX-2021-4305
github.com/advisories/GHSA-p6j9-7xhc-rhwp
github.com/medialize/URI.js/commit/a1ad8bcbc39a4d136d7e252e76e957f3ece70839
github.com/medialize/URI.js/releases/tag/v1.19.6
github.com/medialize/URI.js/security/advisories/GHSA-p6j9-7xhc-rhwp
nvd.nist.gov/vuln/detail/CVE-2021-27516
CVSS2
Attack Vector
NETWORK
Attack Complexity
LOW
Authentication
NONE
Confidentiality Impact
PARTIAL
Integrity Impact
NONE
Availability Impact
NONE
AV:N/AC:L/Au:N/C:P/I:N/A:N
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
NONE
Availability Impact
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS
Percentile
68.3%