CVE-2026-91920

6.5 MEDIUM 0.2% exploit odds No fix listed Memory safety Web app

What it is

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.

At a glance

Exploitability: Can be exploited over the network without logging in. Limited direct impact.
Exploit odds: 0.2% chance of exploitation in the next 30 days (EPSS).
Fix: No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

2026-09-15 10:20 UTC ReservedThe CVE id was reserved by its CNA
2026-10-30 02:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-11-06 02:17 UTC Last updatedMost recent change to the record

Details

Published: 2026-10-30 02:17 UTC
Last modified: 2026-11-06 02:17 UTC
Exploit probability: 0.2% · EPSS, next 30 days
Weakness: CWE-444
Record status: Awaiting Analysis

Attack profile CVSS 3.1 · 6.5

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: Low

Raw vector

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

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References

NVD record · CVE.org record