CVE-2025-15104
low-risk
Published 2026-01-16
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).
Do I need to act?
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0.03% chance of exploitation
EPSS score — low exploit probability
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Not on CISA KEV list
No confirmed active exploitation reported to CISA
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Patch status unknown
Check vendor advisories for fix availability and mitigation guidance
5
CVSS 5.3/10
Medium
NETWORK
/ LOW complexity
Affected Products (1)
Validator
Affected Vendors
References (3)
26
/ 100
low-risk
Severity
21/34 · High
Exploitability
0/34 · Minimal
Exposure
5/34 · Minimal