Vulnerability Description
A flaw was found in Undertow, an HTTP server, within its HTTP response header writing path. The `writeString()` method performs a silent narrowing cast from 16-bit Unicode characters to 8-bit bytes when writing HTTP response header values. A remote attacker can exploit this by supplying specific Unicode characters in user-controlled input that an application places into response headers. This can lead to the truncation of these characters into ASCII control characters or special symbols, potentially resulting in limited integrity impact or information disclosure if the application does not properly sanitize user input.
CVSS Score
MEDIUM
Related Weaknesses (CWE)
References
- https://access.redhat.com/security/cve/CVE-2026-19879
- https://bugzilla.redhat.com/show_bug.cgi?id=2516038
FAQ
What is CVE-2026-19879?
CVE-2026-19879 is a vulnerability with a CVSS score of 5.3 (MEDIUM). A flaw was found in Undertow, an HTTP server, within its HTTP response header writing path. The `writeString()` method performs a silent narrowing cast from 16-bit Unicode characters to 8-bit bytes wh...
How severe is CVE-2026-19879?
CVE-2026-19879 has been rated MEDIUM with a CVSS base score of 5.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-19879?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.