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CVE-2025-15104

Nu Html Checker (validator.nu) - Restriction bypass vulnerability allowing local SSRF

6.9 Medium

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).

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
None

Exploit likelihood

0.46%Up 0.4 points since Jan 17, 2026
90%50%10%1%

What each source reports

CVE List Score used 6.9

Nu Html Checker (validator.nu) - Restriction bypass vulnerability allowing local SSRF

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).

Record
CVE-2025-15104
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N
Weakness
CWE-918
Updated
2026-11-02
EUVDEUVD-2026-2919 6.9

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).

Record
EUVD-2026-2919
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-fccg-7w3p-w66f 5.5

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).

Record
GHSA-fccg-7w3p-w66f
CVSS 4.0
5.5 MediumCVSS: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-918
Updated
2026-11-02
NVD 6.9

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).

Record
CVE-2025-15104
CVSS 4.0
6.9 MediumCVSS: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:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-918
Updated
2026-11-02
OSVDEBIAN-CVE-2025-15104 5.3

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).

Record
DEBIAN-CVE-2025-15104
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
OSVGHSA-fccg-7w3p-w66f 5.5

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).

Record
GHSA-fccg-7w3p-w66f
CVSS 4.0
5.5 MediumCVSS: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-918
Updated
2026-11-02
OSVUBUNTU-CVE-2025-15104 6.9

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).

Record
UBUNTU-CVE-2025-15104
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
nu.validator:validator
Maven
through 26.1.11 None known
vnu-jar
npm
through 26.1.11 None known
vnu
Debian:14
All versions, plus listed versions
23.4.11+dfsg-123.4.11+dfsg-223.4.11+dfsg-323.4.11+dfsg-423.4.11+dfsg-526.5.2.1+dfsg-126.5.2.1+dfsg-226.8.15.1+dfsg-1
None known
nu.validator:validator
Maven
through 26.1.11, plus listed versions
15.3.1015.3.1115.3.1215.3.1415.3.28
Show 45 moreShow less
15.4.1215.6.2916.1.116.3.316.6.1816.6.2016.6.2917.0.017.0.117.1.017.11.017.11.117.2.017.2.117.3.017.7.017.9.018.11.518.3.018.7.2218.7.2318.8.2920.3.1620.6.3020.7.225.10.2725.10.2925.10.3025.10.3125.11.125.11.1725.11.1925.11.225.11.2025.11.2525.11.2725.11.2825.11.2925.11.325.11.3025.11.425.11.525.11.625.11.725.11.8
None known
vnu
Ubuntu:26.10
All versions, plus listed versions
23.4.11+dfsg-526.5.2.1+dfsg-126.5.2.1+dfsg-226.8.15.1+dfsg-1
None known

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2025-15104 is a medium vulnerability (CVSS 6.9) in The Nu Html Checker Nu Html Checker, published January 16, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.46%, the 40th percentile. No source names a fixed version.

References

This page doesn't list everything

Left out here: 34 versions. The JSON record has them.

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