What’s Vulnerable › Vulnerabilities

CVE-2026-19879: Io.undertow/undertow: undertow: http response header integrity issue due to character truncation

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-14 · updated 2026-08-14
• Weakness: CWE-681

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.

Affected products

• Red Hat build of Apache Camel for Spring Boot 4: all versions
• Red Hat Enterprise Linux 10: all versions
• Red Hat Enterprise Linux 8: all versions
• Red Hat Enterprise Linux 9: all versions
• Red Hat JBoss Enterprise Application Platform 7: all versions
• Red Hat JBoss Enterprise Application Platform 8: all versions
• Red Hat JBoss Enterprise Application Platform Expansion Pack: all versions
• Red Hat Single Sign-On 7: all versions

References

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

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