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.
Fix
Nothing published yet: no patch, vendor advisory or mitigation reference on NVD, no vendor advisory in the News for this CVE, not in CISA's KEV, no fixed package version. BaselineWatch does not guess at one.
Change history 1
- First seenCVSS 6.5 · red hatNVD modified 2026-10-30 01:16
Affected (CPE criteria) 0
NVD has not attached CPE configurations yet.
References 2
- https://access.redhat.com/security/cve/CVE-2026-91920 vdb-entry, x_refsource_redhat
- https://bugzilla.redhat.com/show_bug.cgi?id=2528758 issue-tracking, x_refsource_redhat