CVE-2026-91920
Medium · 6.5CVSS
6.5
EPSS
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Published
Oct 30, 2026
CISA due date
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The record
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
| Ecosystem | Package | Introduced | Fixed |
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Related vulnerabilities
- CVE-2026-55613 uhttpd is a small HTTP server. CWE-444
- CVE-2026-55614 uhttpd is a small HTTP server. CWE-444
- CVE-2026-55612 uhttpd is a small HTTP server. CWE-444
- CVE-2026-116127 Starlet versions before 0.33 for Perl send a body in responses to HEAD requests… CWE-444
- CVE-2026-118264 Echo is a Go web framework. CWE-444
- CVE-2026-103995 Response body and chunk parsing would handle non-hex or negative integers incorrectly… CWE-444
- CVE-2026-115823 Starman versions before 0.4019 for Perl send response bodies for HEAD requests… CWE-444
- CVE-2026-115877 Twisted is an event-based framework for internet applications, supporting Python 3.6+. CWE-444