Validator.nu Nu Html Checker 127.0.0.1 server-side request forgery

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
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CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
5.7$0-$5k0.00

Summaryinfo

A vulnerability was found in Validator.nu Nu Html Checker 127.0.0.1. It has been rated as critical. This issue affects some unknown processing. Performing a manipulation results in server-side request forgery. This vulnerability is known as CVE-2025-15104. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability was found in Validator.nu Nu Html Checker 127.0.0.1. It has been classified as critical. This affects an unknown function. The manipulation with an unknown input leads to a server-side request forgery vulnerability. CWE is classifying the issue as CWE-918. The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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).

The weakness was published by Oscar Uribe. The advisory is shared at fluidattacks.com. This vulnerability is uniquely identified as CVE-2025-15104 since 12/26/2025. The exploitability is told to be easy. It is possible to initiate the attack remotely. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 01/24/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Vendor

Name

Version

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 5.8
VulDB Meta Temp Score: 5.7

VulDB Base Score: 6.3
VulDB Temp Score: 6.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 5.3
NVD Vector: 🔒

CVSSv2info

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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Server-side request forgery
CWE: CWE-918
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

12/26/2025 CVE reserved
01/16/2026 +21 days Advisory disclosed
01/16/2026 +0 days VulDB entry created
01/24/2026 +8 days VulDB entry last update

Sourcesinfo

Advisory: fluidattacks.com
Researcher: Oscar Uribe
Status: Not defined

CVE: CVE-2025-15104 (🔒)
GCVE (CVE): GCVE-0-2025-15104
GCVE (VulDB): GCVE-100-341565

Entryinfo

Created: 01/16/2026 15:54
Updated: 01/24/2026 15:04
Changes: 01/16/2026 15:54 (65), 01/24/2026 15:04 (11)
Complete: 🔍
Cache ID: 216::103

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