CVE-2025-12799 Red Hat CVE debrief

Who should care

Users of Jastow who use a set of combined configuration to allow unescaped characters in URL with embedded Undertow and Jastow should review and update configurations to prevent XSS attacks. This includes operators, platform administrators, vulnerability management teams, and security teams.

Technical summary

A flaw was found in Jastow. Jastow is vulnerable to Cross-Site Scripting (XSS) attack. If using a set of combined configuration to allow unescaped characters in URL with embedded Undertow and Jastow, a server might be vulnerable to improper input handling. This could lead to potential XSS attacks. Users should review and update Jastow configurations to prevent unescaped characters in URLs. Affected product deployments should be confirmed in managed environments, and owners should be assigned for follow-up. The CVE record was published on 2026-07-07T17:16:34.640Z and has not been modified since then. Evidence is limited, and defenders should verify configurations, review compensating controls, and monitor for suspicious activity.

Defensive priority

Medium priority given the CVSS score of 6.5 and the potential for XSS attacks.

Recommended defensive actions

• Review and update Jastow configurations to prevent unescaped characters in URLs.
• Implement proper input handling and validation.
• Monitor for suspicious activity and implement compensating controls.
• Apply vendor remediation if available.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.

Evidence notes

Evidence is limited. Primary official records indicate a potential XSS vulnerability in Jastow. Further review and verification are necessary to confirm affected scope and severity. Defenders should verify configurations, review compensating controls, and monitor for suspicious activity.

Official resources