Nu Html Checker (vnu) contains a Server-Side Request Forgery (SSRF) vulnerability
Nu Html Checker (validator.nu) contains a restriction bypass that allows remote attackers to make the server perform arbitrary HTTP/HTTPS requests to internal resources, including localhost services. While the validator implements hostname-based protections to block direct access to localhost and 127.0.0.1, these controls can be bypassed using DNS rebinding techniques or domains that resolve to loopback addresses.This issue affects The Nu Html Checker (vnu): latest (commit 23f090a11bab8d0d4e698f1ffc197a4fe226a9cd).
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Java / Kotlin (Maven) | nu.validator:validator | <= 26.1.11 | no fix |
| npm package | vnu-jar | <= 26.1.11 | no fix |
References
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N/E:P- Weakness (CWE)
CWE-918- Platform
- Java / Kotlin (Maven), npm
- Package
nu.validator:validator, vnu-jar- Disclosed
- 16.01.2026
- Updated
- 11.10.2026 12:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-fccg-7w3p-w66f - CC BY 4.0
Vulnerability history: nu.validator:validator
All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.
This is the only known vulnerability of this package.
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