CVE-2025-15104
Nu Html Checker (validator.nu) - Restriction bypass vulnerability allowing local SSRF
- State
- Published
- Severity
- 6.9 Medium
- Published
- Jan 16, 2026
- Updated
- Jan 16, 2026
- Reserved
- Dec 26, 2025
Description
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).
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 6.9 Medium | 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 | Fluid Attacks |
Weaknesses
- CWE-918 Server-Side Request Forgery (SSRF)
Affected Products
| Product | Versions |
|---|---|
The Nu Html CheckerThe Nu Html Checker |
|
References
- https://fluidattacks.com/advisories/europethird-party-advisory
- https://github.com/validator/validatorproduct
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