Undertow: undertow: chunkreader message length permits chunk-size overflow
cve-program · CVE-2026-91920
PublishedA 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.
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CVE-2026-91920 · CVE overview and exploitation status
cve-program · CVE-2026-91920
Related changes
Linked by CVE identifier- Undertow: undertow: chunkreader message length permits chunk-size overflow · Affected-version evidence changed · 6 Nov 2026
- Undertow: undertow: chunkreader message length permits chunk-size overflow · Affected-version evidence changed · 3 Nov 2026
- Undertow: undertow: chunkreader message length permits chunk-size overflow · Newly collected advisory · 30 Oct 2026