CVE-2026-49855
Published:July 14, 2026
Updated:July 21, 2026
Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.6, Tornado gzip decompression routines processed limited-size chunks but did not enforce an overall limit on accumulated decompressed chunks, allowing a malicious server accessed by SimpleAsyncHTTPClient or an HTTPServer configured with decompress_request=True to consume effectively unlimited memory. This issue is fixed in version 6.5.6.
Affected Packages
tornado (CONDA):
Affected version(s) >=2.3 <6.5.6Fix Suggestion:
Update to version 6.5.6tornado (CONDA):
Affected version(s) >=2.3 <6.5.6Fix Suggestion:
Update to version 6.5.6https://github.com/tornadoweb/tornado.git (GITHUB):
Affected version(s) >=v1.0.0 <v6.5.6Fix Suggestion:
Update to version v6.5.6tornado (PYTHON):
Affected version(s) >=0.2 <6.5.6Fix Suggestion:
Update to version 6.5.6Related Resources (7)
Do you need more information?
Contact UsCVSS v4
Base Score:
8.7
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
NONE
Vulnerable System Availability
HIGH
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
7.5
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Weakness Type (CWE)
Improper Handling of Highly Compressed Data (Data Amplification)
EPSS
Base Score:
0.69