CVE-2026-91920 — MEDIUM (6.5)

Vulnerability 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.

CVSS Score

6.5

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality

NONE

Integrity

LOW

Availability

LOW

Related Weaknesses (CWE)

CWE-444

References

FAQ

What is CVE-2026-91920?

CVE-2026-91920 is a vulnerability with a CVSS score of 6.5 (MEDIUM). 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 si...

How severe is CVE-2026-91920?

CVE-2026-91920 has been rated MEDIUM with a CVSS base score of 6.5/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-91920?

Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.