CVE-2026-91920Medium· 6.5▾ SunlitA 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 s…
▾ Sunlit zone — Low / medium · no exploitation signal
impact 35.8 · likelihood 0 · exploitation 0
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Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake. The CVSS score shown above comes from the assigning CNA record, not NVD.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via CVEORG
Last analysed / modified upstream
0.2%
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.
undertow-servlet (all versions)pki-core:10.6/resteasypki-deps:10.6/resteasyresteasyundertow-servletjboss-eap-7/eap74-els-openjdk11-openshift-rhel8 (all versions)jboss-eap-7/eap74-els-openjdk17-openshift-rhel8 (all versions)jboss-eap-7/eap74-els-openjdk8-openshift-rhel8 (all versions)undertow-servlet (all versions)undertow-servlet (all versions)undertow-servletundertow-servlet (all versions)Refer to the linked advisories for vendor-supplied fixes and affected version ranges.
Connected by shared product, vendor, weakness, or advisory.
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