CVE-2025-15104
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).
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
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 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 - 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 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 - 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 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/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 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/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 Medium
CVSS: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 Medium
CVSS: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 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/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 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 - CVSS 3.1
- 5.3 Medium
CVSS: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
| Package | Affected | Fixed |
|---|---|---|
nu.validator:validatorMaven |
through 26.1.11 | None known |
vnu-jarnpm |
through 26.1.11 | None known |
vnuDebian: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:validatorMaven |
through 26.1.11, plus listed versions 15.3.1015.3.1115.3.1215.3.1415.3.28 Show 45 moreShow less15.4.1215.6.2916.1.116.3.316.6.1816.6.2016.6.2917.0.017.0.117.1.017.11.017.11.117.2.017.2.117.3.017.7.017.9.018.11.518.3.018.7.2218.7.2318.8.2920.3.1620.6.3020.7.225.10.2725.10.2925.10.3025.10.3125.11.125.11.1725.11.1925.11.225.11.2025.11.2525.11.2725.11.2825.11.2925.11.325.11.3025.11.425.11.525.11.625.11.725.11.8 |
None known |
vnuUbuntu: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
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE 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
fluidattacks.com/advisories/europe
github.com/validator/validator
nvd.nist.gov/vuln/detail/CVE-2025-15104
github.com/advisories/GHSA-fccg-7w3p-w66f
security-tracker.debian.org/tracker/CVE-2025-15104
ubuntu.com/security/CVE-2025-15104
cve.org/CVERecord?id=CVE-2025-15104
github.com/validator/validator/issues/2033
github.com/validator/validator/commit/b95c4190258db2769cff67cc09d323432bd7a99e
Left out here: 34 versions. The JSON record has them.