Medium [CVE-2026-19879] HTTP response header integrity issue due to character truncation
This medium-severity Red Hat Linux advisory covers CVE-2026-19879 affecting Red Hat build of Apache Camel for Spring Boot 4, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8.
Android app · Google Play
Monitor future Red Hat Linux CVEs from your phone.
Choose a whole vendor or a precise platform, then receive matching security advisories by phone notification, email, or both. Coverage follows 32 official vendor sources and 160+ reviewed platform categories.
Summary
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.
This Moderate impact defense-in-depth flaw in Undertow's HTTP response header handling occurs when applications place unsanitized user-controlled Unicode input into response headers.
While Undertow prevents HTTP response splitting, the silent truncation of characters to ASCII control characters or special symbols could pose a risk in applications that reflect these header values without proper validation. Red Hat severity: Moderate — CVSS 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N).
Weakness: CWE-681.
Affected products named by the advisory: 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; and 6 more.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Mitigation checklist
- Applications utilizing Undertow should implement robust input validation and sanitization for all user-controlled data before it is placed into HTTP response headers. It is recommended to restrict header values to printable ASCII characters (0x20–0x7E) at the application level. Where available, use framework-provided header-safe encoding mechanisms to ensure proper handling of special characters.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Discussion(0)
No comments yet. Share field notes, upgrade gotchas, or questions — verify against the vendor advisory before acting on community advice.
Sign in to join the discussion.