CVE-2026-91920

Undertow: undertow: chunkreader message length permits chunk-size overflow

Published Oct 30, 2026 CVSS 3.1 · 6.5 Medium EPSS < 1% KEV · Not listed
Description
A flaw was found in the ChunkReader component of the Undertow web server, which is used to handle chunked transfer encoding in HTTP requests. The issue occurs because a security check for the chunk size is performed before the value is shifted, allowing a specifically crafted 15-digit chunk size to bypass the limit and overflow into internal state flags. This can cause the server to terminate a request body prematurely and interpret the remaining data as a separate, smuggled request.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
CPEs cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
cpe:/a:redhat:enterprise_linux:8
cpe:/a:redhat:enterprise_linux:9
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Title undertow: undertow: ChunkReader message length permits chunk-size overflow Undertow: undertow: chunkreader message length permits chunk-size overflow
First Time appeared Redhat
Redhat camel Spring Boot
Redhat enterprise Linux
Redhat jboss Enterprise Application Platform
Redhat jboss Fuse
Redhat jbosseapxp
Redhat red Hat Single Sign On
CPEs cpe:/a:redhat:camel_spring_boot:4
cpe:/a:redhat:jboss_enterprise_application_platform:7
cpe:/a:redhat:jboss_enterprise_application_platform:8
cpe:/a:redhat:jboss_fuse:7
cpe:/a:redhat:jbosseapxp
cpe:/a:redhat:red_hat_single_sign_on:7
cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
Vendors & Products Redhat
Redhat camel Spring Boot
Redhat enterprise Linux
Redhat jboss Enterprise Application Platform
Redhat jboss Fuse
Redhat jbosseapxp
Redhat red Hat Single Sign On
References
Type Values Removed Values Added
Description A flaw was found in the ChunkReader component of the Undertow web server, which is used to handle chunked transfer encoding in HTTP requests. The issue occurs because a security check for the chunk size is performed before the value is shifted, allowing a specifically crafted 15-digit chunk size to bypass the limit and overflow into internal state flags. This can cause the server to terminate a request body prematurely and interpret the remaining data as a separate, smuggled request.
Title undertow: undertow: ChunkReader message length permits chunk-size overflow
Weaknesses CWE-444
References
Metrics threat_severity

None

cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L'}

threat_severity

Moderate

Weaknesses

Sources

Status
PUBLISHED
Assigner
redhat
Published
Updated
Nov 6, 2026, 1:46 AM
Reserved
Sep 15, 2026, 10:20 AM
Status
Awaiting Analysis
Published
Oct 30, 2026, 2:17 AM
Modified
Nov 6, 2026, 2:17 AM
Severity
Moderate
Public date
Oct 29, 2026, 12:11 PM