CVE-2026-66370: Software Security Vulnerability Vulnerability

MODERATE
Advisory Identifier: GHSA-r8xc-fmjg-37c5
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CVSS 6.1
CWE-601
Published
Advisory Summary

CVE-2026-66370 is a MODERATE (CVSS 6.1) security vulnerability vulnerability (CWE-601: URL Redirection to Untrusted Site ('Open Redirect')) affecting Software libraries in the Maven ecosystem. The weakness occurs when the web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-66370 at a Glance

CVE Identifier CVE-2026-66370
GHSA Identifier GHSA-r8xc-fmjg-37c5
Severity MODERATE
CVSS v3.1 Base Score 6.1
CWE Classification CWE-601: URL Redirection to Untrusted Site ('Open Redirect')
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 6.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Changed (S:C)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-66370

To remediate this vulnerability, upgrade all affected Software dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-66370, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree

Analyze the terminal output to locate any version of Software in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The mvn dependency:tree command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect'), where the web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect. In Software, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

URL Redirection to Untrusted Site ('Open Redirect') vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows an unauthenticated remote attacker to retarget a form already on the rendering page and receive whatever the victim submits, including credentials, via the form and formaction attributes on an <input> element in sanitized HTML. HTML's form attribute associates an input with any form on the page by its id even when the input sits outside that form, and formaction on a submit control overrides the owning form's action. Neither attribute receives a scheme check, so an absolute cross-origin URL survives sanitizing. No script executes. The scrubber allows neither form nor button, so the attacker cannot introduce a form of their own and the rendering page must already contain a form carrying an id. This issue affects html_sanitize_ex: from 0.3.1 before 1.5.3.

References

GitHub Advisory / Wiki ADVISORY
https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-w3f9-jjhw-wwvq
NVD — CVE-2026-66370 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-66370
Security Fix Commit FIX COMMIT
https://github.com/rrrene/html_sanitize_ex/commit/21394e758cb0ffe12fb9953c30fdedc6016c8f9e
Security Fix Commit FIX COMMIT
https://github.com/rrrene/html_sanitize_ex/commit/a1e804ed997e780ea71d14393cf2f701330553a6
cna.erlef.org/cves/cve-2026-66370... WEB
https://cna.erlef.org/cves/CVE-2026-66370.html
osv.dev/vulnerability/eef-c... WEB
https://osv.dev/vulnerability/EEF-CVE-2026-66370

Frequently Asked Questions

What is CVE-2026-66370?
CVE-2026-66370 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-601: URL Redirection to Untrusted Site ('Open Redirect').
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-66370?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-66370?
CVE-2026-66370 has a CVSS v3.1 base score of 6.1 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2026-66370?
CVE-2026-66370 is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect') (The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.).
How can I check Maven dependencies for CVE-2026-66370?
Run the dependency tree command: 'mvn dependency:tree'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-r8xc-fmjg-37c5",
  "modified" : "2026-08-19T12:32:21Z",
  "published" : "2026-08-06T18:30:49Z",
  "aliases" : [ "CVE-2026-66370" ],
  "details" : "URL Redirection to Untrusted Site ('Open Redirect') vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows an unauthenticated remote attacker to retarget a form already on the rendering page and receive whatever the victim submits, including credentials, via the form and formaction attributes on an <input> element in sanitized HTML. HTML's form attribute associates an input with any form on the page by its id even when the input sits outside that form, and formaction on a submit control overrides the owning form's action. Neither attribute receives a scheme check, so an absolute cross-origin URL survives sanitizing.\n\nNo script executes. The scrubber allows neither form nor button, so the attacker cannot introduce a form of their own and the rendering page must already contain a form carrying an id.\n\nThis issue affects html_sanitize_ex: from 0.3.1 before 1.5.3.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:H/SI:L/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"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-w3f9-jjhw-wwvq"
  }, {
    "type" : "ADVISORY",
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  }, {
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  }, {
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    "url" : "https://github.com/rrrene/html_sanitize_ex/commit/a1e804ed997e780ea71d14393cf2f701330553a6"
  }, {
    "type" : "WEB",
    "url" : "https://cna.erlef.org/cves/CVE-2026-66370.html"
  }, {
    "type" : "WEB",
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  } ],
  "database_specific" : {
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    "severity" : "MODERATE",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-08-06T16:16:48Z"
  }
}