CVE-2026-19879
Io.undertow/undertow: undertow: http response header integrity issue due to character truncation
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.
INFO
Published Date :
Aug. 14, 2026, 3:17 p.m.
Last Modified :
Aug. 14, 2026, 3:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-19879
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | 53f830b8-0a3f-465b-8143-3b8a9948e749 | ||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update Undertow to a version that correctly handles character encoding.
- Sanitize user-supplied input before placing it in headers.
- Validate character encoding for header values.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-19879.
| URL | Resource |
|---|---|
| https://access.redhat.com/security/cve/CVE-2026-19879 | |
| https://bugzilla.redhat.com/show_bug.cgi?id=2516038 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-19879 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-19879
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-19879 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-19879 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Aug. 14, 2026
Action Type Old Value New Value Added Affected [{'cpes': ['cpe:/a:redhat:camel_spring_boot:4'], 'vendor': 'Red Hat', 'product': 'Red Hat build of Apache Camel for Spring Boot 4', 'packageName': 'undertow-core', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:camel_spring_boot:4'], 'vendor': 'Red Hat', 'product': 'Red Hat build of Apache Camel for Spring Boot 4', 'packageName': 'undertow-parent', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:camel_spring_boot:4'], 'vendor': 'Red Hat', 'product': 'Red Hat build of Apache Camel for Spring Boot 4', 'packageName': 'undertow-servlet', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:camel_spring_boot:4'], 'vendor': 'Red Hat', 'product': 'Red Hat build of Apache Camel for Spring Boot 4', 'packageName': 'undertow-websockets-jsr', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:10'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 10', 'packageName': 'moditect', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8', 'packageName': 'pki-core:10.6/resteasy', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8', 'packageName': 'pki-deps:10.6/resteasy', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:9'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9', 'packageName': 'resteasy', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:jboss_enterprise_application_platform:7'], 'vendor': 'Red Hat', 'product': 'Red Hat JBoss Enterprise Application Platform 7', 'packageName': 'jboss-eap-7/eap74-els-openjdk11-openshift-rhel8', 'collectionURL': 'https://access.redhat.com/jbossnetwork/restricted/listSoftware.html', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:jboss_enterprise_application_platform:7'], 'vendor': 'Red Hat', 'product': 'Red Hat JBoss Enterprise Application Platform 7', 'packageName': 'jboss-eap-7/eap74-els-openjdk17-openshift-rhel8', 'collectionURL': 'https://access.redhat.com/jbossnetwork/restricted/listSoftware.html', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:jboss_enterprise_application_platform:7'], 'vendor': 'Red Hat', 'product': 'Red Hat JBoss Enterprise Application Platform 7', 'packageName': 'jboss-eap-7/eap74-els-openjdk8-openshift-rhel8', 'collectionURL': 'https://access.redhat.com/jbossnetwork/restricted/listSoftware.html', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:jboss_enterprise_application_platform:7'], 'vendor': 'Red Hat', 'product': 'Red Hat JBoss Enterprise Application Platform 7', 'packageName': 'undertow-core', 'collectionURL': 'https://access.redhat.com/jbossnetwork/restricted/listSoftware.html', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:jboss_enterprise_application_platform:7'], 'vendor': 'Red Hat', 'product': 'Red Hat JBoss Enterprise Application Platform 7', 'packageName': 'undertow-parent', 'collectionURL': 'https://access.redhat.com/jbossnetwork/restricted/listSoftware.html', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:jboss_enterprise_application_platform:7'], 'vendor': 'Red Hat', 'product': 'Red Hat JBoss Enterprise Application Platform 7', 'packageName': 'undertow-servlet', 'collectionURL': 'https://access.redhat.com/jbossnetwork/restricted/listSoftware.html', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:jboss_enterprise_application_platform:7'], 'vendor': 'Red Hat', 'product': 'Red Hat JBoss Enterprise Application Platform 7', 'packageName': 'undertow-websockets-jsr', 'collectionURL': 'https://access.redhat.com/jbossnetwork/restricted/listSoftware.html', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:jboss_enterprise_application_platform:8'], 'vendor': 'Red Hat', 'product': 'Red Hat JBoss Enterprise Application Platform 8', 'packageName': 'undertow-core', 'collectionURL': 'https://access.redhat.com/jbossnetwork/restricted/listSoftware.html', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:jboss_enterprise_application_platform:8'], 'vendor': 'Red Hat', 'product': 'Red Hat JBoss Enterprise Application Platform 8', 'packageName': 'undertow-servlet', 'collectionURL': 'https://access.redhat.com/jbossnetwork/restricted/listSoftware.html', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:jboss_enterprise_application_platform:8'], 'vendor': 'Red Hat', 'product': 'Red Hat JBoss Enterprise Application Platform 8', 'packageName': 'undertow-websockets-jsr', 'collectionURL': 'https://access.redhat.com/jbossnetwork/restricted/listSoftware.html', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:jbosseapxp'], 'vendor': 'Red Hat', 'product': 'Red Hat JBoss Enterprise Application Platform Expansion Pack', 'packageName': 'undertow-core', 'collectionURL': 'https://access.redhat.com/jbossnetwork/restricted/listSoftware.html', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:jbosseapxp'], 'vendor': 'Red Hat', 'product': 'Red Hat JBoss Enterprise Application Platform Expansion Pack', 'packageName': 'undertow-servlet', 'collectionURL': 'https://access.redhat.com/jbossnetwork/restricted/listSoftware.html', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:jbosseapxp'], 'vendor': 'Red Hat', 'product': 'Red Hat JBoss Enterprise Application Platform Expansion Pack', 'packageName': 'undertow-websockets-jsr', 'collectionURL': 'https://access.redhat.com/jbossnetwork/restricted/listSoftware.html', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:red_hat_single_sign_on:7'], 'vendor': 'Red Hat', 'product': 'Red Hat Single Sign-On 7', 'packageName': 'undertow-core', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:red_hat_single_sign_on:7'], 'vendor': 'Red Hat', 'product': 'Red Hat Single Sign-On 7', 'packageName': 'undertow-servlet', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:red_hat_single_sign_on:7'], 'vendor': 'Red Hat', 'product': 'Red Hat Single Sign-On 7', 'packageName': 'undertow-websockets-jsr', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}] Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N Added CWE CWE-681 Added Reference https://access.redhat.com/security/cve/CVE-2026-19879 Added Reference https://bugzilla.redhat.com/show_bug.cgi?id=2516038