CVE-2026-5680

A flaw was found in Undertow. A remote attacker could exploit this vulnerability by sending specially crafted WebSocket messages with permessage-deflate negotiated. This could lead to excessive memory consumption due to the PerMessageDeflateFunction.largerBuffer() method using exponential doubling, resulting in a Denial of Service (DoS) for the affected application.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, configure the PerMessageDeflateHandshake to limit the maximum decompressed buffer size. This can be achieved by setting the maxDecompressedBufferSize parameter to a reasonable value (e.g., 10 MB) in the PerMessageDeflateHandshake constructor. This action may require a restart of the affected application or service to take effect.