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Fencer Intel
medium 6.1

CVE-2025-56200 json

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

published last yr. modified last mo. also GHSA-9965-vmph-33xx , EUVD-2025-31764

cvss
6.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 25%
public exploits
0
none known

Summary

A URL validation bypass vulnerability exists in validator.js through version 13.15.15. 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.

Patch / fix

  • npm validator 13.15.20

Is CVE-2025-56200 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
last yr.

Exploit prediction

0.32% chance of exploitation in the next 30 days, higher than 25% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • gist.github.com https://gist.github.com/junan-98/a93130505b258b9e4ec9f393e7533596 referenced PoC, tagged "exploit" by a source, unverified
  • gist.github.com https://gist.github.com/junan-98/27ae092aa40e2a057d41a0f95148f666 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CISA ADP 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CNA 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
GitHub 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
npm validator
<13.15.20
13.15.20

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.