Improper Handling of Highly Compressed Data (Data Amplification) Affecting tornado package, versions [,6.5.6)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
Do your applications use this vulnerable package?
In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.
Test your applications- Snyk IDSNYK-PYTHON-TORNADO-17356108
- published17 Jun 2026
- disclosed15 Jun 2026
- creditYuichiro Kedashiro (keda)
Introduced: 15 Jun 2026
CVE-2026-49855 (opens in a new tab)How to fix?
Upgrade tornado to version 6.5.6 or higher.
Overview
tornado is a Python web framework and asynchronous networking library, originally developed at FriendFeed.
Affected versions of this package are vulnerable to Improper Handling of Highly Compressed Data (Data Amplification) in the AsyncHTTPClient. An attacker can cause excessive memory consumption by sending a response with a small compressed size that decompresses to a very large payload, leading to resource exhaustion.
Note: This is only exploitable if decompress_request=True is set on HTTPServer.
Workaround
This vulnerability can be mitigated by setting decompress_response=False or using CurlAsyncHTTPClient.