Overflow Vulnerability in Undertow Web Server ChunkReader Component
CVE-2026-91920

6.5MEDIUM

Key Information:

Vendor

Red Hat
Status
Red Hat Build Of Apache Camel For Spring Boot 4
Red Hat Enterprise Linux 8
Red Hat Enterprise Linux 9
Red Hat Fuse 7
Vendor
CVE Published:
30 October 2026

What is CVE-2026-91920?

A flaw exists in the ChunkReader component of the Undertow web server that handles chunked transfer encoding. This vulnerability arises from a security check that is incorrectly positioned, allowing a specially crafted 15-digit chunk size to bypass normal limits and potentially overflow internal state flags. As a result, the server may terminate a request body prematurely, interpreting the remaining data as a separate, unintended request. Such behavior can lead to critical security issues, including HTTP request smuggling attacks.

References

https://access.redhat.com/security/cve/CVE-2026-91920
vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2528758
issue-trackingx_refsource_REDHAT

CVSS V3.1

Score:
6.5
Severity:
MEDIUM
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Red Hat would like to thank Arpit Jain for reporting this issue.
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