validator.js has a URL validation bypass vulnerability in its isURL function

Description

A URL validation bypass vulnerability exists in validator.js prior to version 13.15.20. The isURL() function uses '://' as a delimiter to parse protocols, while browsers use ':' as the delimiter. This parsing difference allows attackers to bypass protocol and domain validation by crafting URLs leading to XSS and Open Redirect attacks.

Basic information

Type
reviewed
Severity
medium
Advisory on GitHub
Open advisory ↗
Repository advisory
Source code
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Published (advisory)
2025-09-30 18:30:25 UTC
Updated
2025-10-27 12:53:01 UTC
GitHub reviewed
2025-10-13 20:08:58 UTC
NVD published
2025-09-30 18:15:50 UTC

EPSS Score

Score Percentile
0.04% 13.61%

CVSS Scores

Base score Version Severity Vector
6.1 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.

Identifiers

CWEs

CWE id Name
CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Credits

  • G-Rath (analyst)
  • Moumouls (analyst)
  • aleyipsoftwire (analyst)

Affected packages (1)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
npm validator < 13.15.20 13.15.20

References

cvelogic Threat Intelligence