CVE-2026-19879
mediumpriority · track · 0EPSS 0.004 · 33 %ileDEEUUSEPSS · scored 2026-10-27
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
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
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affected products (1)
Products and version ranges known to be affected.
advisories (1)
Vendor and ecosystem advisories describing this.
- WID-SEC-W-2026-2862Red Hat Undertow: Schwachstelle ermöglicht Manipulation von DateienDeutsch2026-08-16csaf · cert_bundDE
Ein entfernter, anonymer Angreifer kann eine Schwachstelle in Red Hat Undertow ausnutzen, um Dateien zu manipulieren.
also known as (2)
Other names and identifiers for this entity.
sources
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references (4)
External citations — patches, advisories, analysis.
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