Flaw in Undertow HTTP Server Affects Multiple Applications
CVE-2026-19879

5.3MEDIUM

Key Information:

Vendor

Red Hat
Status
Red Hat Build Of Apache Camel For Spring Boot 4
Red Hat Enterprise Linux 10
Red Hat Enterprise Linux 8
Red Hat Enterprise Linux 9
Vendor
CVE Published:
14 August 2026

What is CVE-2026-19879?

A flaw exists in the Undertow HTTP server related to the handling of HTTP response headers. Specifically, the writeString() method allows a silent narrowing cast from 16-bit Unicode to 8-bit bytes, making it susceptible to exploitation by remote attackers. By injecting carefully crafted Unicode characters into user-controlled input that subsequently becomes part of response headers, attackers can cause truncation to ASCII control characters or special symbols. If the application does not adequately sanitize user input, this vulnerability may lead to information disclosure or other forms of integrity impact.

References

https://access.redhat.com/security/cve/CVE-2026-19879
vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2516038
issue-trackingx_refsource_REDHAT

CVSS V3.1

Score:
5.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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