Vulnerability · Published Oct 30, 2026 · Assigned by redhat

CVE-2026-91920Undertow: undertow: chunkreader message length permits chunk-size overflow

Medium 6.5

In plain English

A medium-severity security flaw in Red Hat build of Apache Camel for Spring Boot 4 from Red Hat. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 15% of all known vulnerabilities).

Severity (CVSS 3.1)6.5Medium

Exploit odds (30 days)0.2%top 85.4% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:14	undertow	no fix listed	DEBIAN-CVE-2026-91920
Ubuntu:26.04:LTS	undertow	no fix listed	UBUNTU-CVE-2026-91920
Ubuntu:26.10	undertow	no fix listed	UBUNTU-CVE-2026-91920

Affected products (as reported)

Vendor	Product	Versions
Red Hat	Red Hat build of Apache Camel for Spring Boot 4	see references
Red Hat	Red Hat Enterprise Linux 8	see references
Red Hat	Red Hat Enterprise Linux 8	see references
Red Hat	Red Hat Enterprise Linux 9	see references
Red Hat	Red Hat Fuse 7	see references
Red Hat	Red Hat JBoss Enterprise Application Platform 7	see references
Red Hat	Red Hat JBoss Enterprise Application Platform 7	see references
Red Hat	Red Hat JBoss Enterprise Application Platform 7	see references
Red Hat	Red Hat JBoss Enterprise Application Platform 7	see references
Red Hat	Red Hat JBoss Enterprise Application Platform 8	see references
Red Hat	Red Hat JBoss Enterprise Application Platform Expansion Pack	see references
Red Hat	Red Hat Single Sign-On 7	see references

Weakness: CWE-444 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

References

https://access.redhat.com/security/cve/CVE-2026-91920 vdb-entry, x_refsource_REDHAT
RHBZ#2528758 issue-tracking, x_refsource_REDHAT