CVE-2026-49855

A flaw was found in Tornado, a Python web framework and asynchronous networking library. Its gzip decompression routines process data in limited-size chunks but do not enforce an overall limit on the total accumulated decompressed data. This vulnerability allows a malicious server to consume effectively unlimited memory, leading to a denial of service, when accessed by a client using SimpleAsyncHTTPClient or an HTTPServer configured with decompress_request set to true.

This Important impact flaw in the Tornado Python web framework allows a malicious server to cause uncontrolled memory consumption by sending highly compressed gzip responses, since the decompression routines do not enforce an overall size limit. This can lead to a denial of service in applications using SimpleAsyncHTTPClient or HTTPServer with decompress_request=True.

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.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.