CVE-2023-1932: Redhat Codeready Studio XSS Vulnerability

CVE-2023-1932 Overview

A flaw was found in hibernate-validator's isValid method in the org.hibernate.validator.internal.constraintvalidators.hv.SafeHtmlValidator class. This vulnerability allows attackers to bypass HTML sanitization by omitting the tag ending in a less-than character. When browsers attempt to render this invalid HTML, it can lead to HTML injection or Cross-Site Scripting (XSS) attacks, potentially compromising user sessions and data integrity.

Critical Impact

Attackers can bypass SafeHtml validation to inject malicious scripts, enabling session hijacking, credential theft, and defacement of web applications built on affected Red Hat and Hibernate products.

Affected Products

• Hibernate hibernate-validator (all versions)
• Red Hat CodeReady Studio 12.0
• Red Hat JBoss Enterprise Application Platform 7.0.0 and Continuous Delivery
• Red Hat OpenStack Platform 13.0
• Red Hat Single Sign-On 7.0

Discovery Timeline

• 2024-11-07 - CVE-2023-1932 published to NVD
• 2025-06-24 - Last updated in NVD database

Technical Details for CVE-2023-1932

Vulnerability Analysis

This vulnerability exists in the SafeHtmlValidator class within Hibernate Validator, a widely-used Java Bean Validation implementation. The isValid method is designed to validate user-supplied HTML content and prevent unsafe HTML elements from being processed. However, the validation logic contains a flaw that allows malformed HTML tags to slip through the sanitization process.

The core issue lies in how the validator parses HTML tag structures. By crafting input that omits the closing greater-than character of a tag and instead uses a less-than character, an attacker can create syntactically invalid HTML that the validator accepts as safe. While this HTML is technically malformed, modern browsers employ error-tolerant parsing that attempts to render such content, potentially executing embedded scripts or displaying injected content.

This bypass is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The network-based attack vector requires user interaction, as victims must view the page containing the malicious content for the attack to execute.

Root Cause

The root cause of this vulnerability is insufficient input validation in the SafeHtmlValidator.isValid() method. The validator fails to properly handle edge cases where HTML tags are intentionally malformed by omitting the closing delimiter. The parsing logic expects well-formed HTML structures and does not account for boundary conditions where tag syntax is deliberately broken to evade detection while remaining renderable by browser HTML parsers.

Attack Vector

This vulnerability is exploitable over the network and requires user interaction to be successful. An attacker can inject malicious HTML content into any field that uses the @SafeHtml annotation for validation. The attack scenario involves:

1. The attacker identifies an input field protected by Hibernate Validator's SafeHtml constraint
2. Malicious HTML is crafted with a tag that omits the closing greater-than character, using a less-than character instead
3. The malformed payload bypasses the isValid() check and is stored or reflected by the application
4. When a victim's browser renders the page, the error-tolerant HTML parser interprets the malformed markup and executes any embedded JavaScript

The vulnerability affects the confidentiality and integrity of user data through potential script execution in the victim's browser context. Applications using SafeHtml validation for user-generated content, comments, or rich text fields are particularly at risk.

Detection Methods for CVE-2023-1932

Indicators of Compromise

• Unusual HTML patterns in user input fields containing incomplete tag structures (missing > characters)
• JavaScript execution attempts from stored user content that should have been sanitized
• Browser console errors indicating malformed HTML rendering in user-contributed content areas
• Unexpected DOM modifications or script inclusions on pages displaying user-generated content

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect malformed HTML patterns, specifically tags ending with < instead of >
• Deploy Content Security Policy (CSP) headers to restrict script execution sources and report violations
• Enable application logging on input validation events and monitor for SafeHtml validation passes on suspicious content
• Utilize browser-based XSS auditors and monitoring tools to detect client-side script injection attempts

Monitoring Recommendations

• Review application logs for unusual HTML content patterns passing through SafeHtml-validated fields
• Monitor for CSP violation reports indicating attempted script execution from untrusted sources
• Implement real-time alerting on web application security events related to input validation bypass attempts
• Conduct periodic security scans of stored user content to identify potentially malicious HTML that bypassed validation

How to Mitigate CVE-2023-1932

Immediate Actions Required

• Audit all application code using the @SafeHtml annotation from Hibernate Validator to identify potentially affected input handling
• Implement additional server-side HTML sanitization using a library such as OWASP Java HTML Sanitizer as a defense-in-depth measure
• Deploy Content Security Policy headers to mitigate the impact of any successful XSS exploitation
• Review and update Web Application Firewall rules to detect and block malformed HTML injection attempts

Patch Information

Organizations should consult the Red Hat CVE-2023-1932 Advisory for the latest patch information and version guidance specific to their deployed Red Hat products. Additional technical details are available in Red Hat Bug Report #1809444. Note that the @SafeHtml annotation has been deprecated in newer versions of Hibernate Validator, and migration to alternative sanitization approaches is recommended.

Workarounds

• Replace usage of @SafeHtml with a dedicated HTML sanitization library such as OWASP Java HTML Sanitizer or jsoup with appropriate safelist configurations
• Implement custom Bean Validation constraints with more robust HTML parsing that accounts for malformed tag structures
• Apply strict Content Security Policy headers with script-src 'self' to prevent execution of injected scripts
• Use output encoding consistently when rendering user-supplied content to prevent browser interpretation of HTML markup

# Example CSP header configuration for Apache
# Add to httpd.conf or .htaccess
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; frame-ancestors 'none';"