CVE-2026-91920
Undertow: undertow: chunkreader message length permits chunk-size overflow
- Published
- Updated
- Reserved
- Assigned by
- redhat
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.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| redhatCNA (assigner) | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L |
| NVDNVD · Awaiting Analysis | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L |
- EPSS (exploitation in 30 days)
- 0.24% · top 85% of all CVEs (5 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.5.
Weakness
Affected products
Red Hat · Red Hat build of Apache Camel for Spring Boot 4
All versions: affected
Red Hat · Red Hat Enterprise Linux 8
All versions: unknown
Red Hat · Red Hat Enterprise Linux 8
All versions: unknown
Red Hat · Red Hat Enterprise Linux 9
All versions: unknown
All versions: unaffected
Red Hat · Red Hat JBoss Enterprise Application Platform 7
All versions: affected
Red Hat · Red Hat JBoss Enterprise Application Platform 7
All versions: affected
Red Hat · Red Hat JBoss Enterprise Application Platform 7
All versions: affected
Red Hat · Red Hat JBoss Enterprise Application Platform 7
All versions: affected
Red Hat · Red Hat JBoss Enterprise Application Platform 8
All versions: affected
Red Hat · Red Hat JBoss Enterprise Application Platform Expansion Pack
All versions: unaffected
Red Hat · Red Hat Single Sign-On 7
All versions: affected
References (2)
- https://access.redhat.com/security/cve/CVE-2026-91920 (opens in a new tab)vdb-entryx_refsource_REDHAT
- RHBZ#2528758 (opens in a new tab)issue-trackingx_refsource_REDHAT
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-91920)Record last updated .