Memory Consumption Vulnerability in Tornado Framework by Tornado Web
CVE-2026-49855

7.5HIGH

Key Information:

Vendor

Tornadoweb

Status
Tornado
Vendor
CVE Published:
14 July 2026

What is CVE-2026-49855?

The Tornado web framework, an asynchronous networking library for Python, has a vulnerability in its gzip decompression routines. Prior to version 6.5.6, the decompression process allows unlimited accumulation of decompressed chunks, potentially resulting in significant memory consumption. This occurs when a malicious server is accessed via SimpleAsyncHTTPClient or when an HTTP server with decompress_request set to true is configured. Users are encouraged to update to version 6.5.6 or later to mitigate this issue.

Affected Version(s)

tornado < 6.5.6

References

https://github.com/tornadoweb/tornado/security/advisories...
x_refsource_CONFIRM
https://github.com/tornadoweb/tornado/pull/3626
x_refsource_MISC
https://github.com/tornadoweb/tornado/commit/ff808b33adc5...
x_refsource_MISC

CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.