CVE-2026-91920

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

MEDIUM
6.5
CVSS Score
Published: October 30, 2026 at 01:16 AM UTC
Updated: October 30, 2026 at 02:17 AM UTC
6 products affected across 1 vendorEnterprise LinuxJBoss Enterprise Application PlatformSingle Sign on

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Severity
MEDIUM6.5
Exploit prediction
EPSS 0.2%

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (2)

VDB Entryx_refsource_REDHAT
Source: cverecord
https://access.redhat.com/security/cve/CVE-2026-91920
Issue Trackingx_refsource_REDHAT
Source: cverecord
https://bugzilla.redhat.com/show_bug.cgi?id=2528758

CVSS

6.5MEDIUMredhat
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
LOW
Vector?

Quick Info

StatusAWAITING ANALYSIS
CWE
CWE-444

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