CVE-2026-49855 | Tornado is a Python web framework and asynchronous networkin… | CVSS 7.5 HIGH

Description

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.

Metadata

CVE ID: CVE-2026-49855
State: PUBLISHED
Assigner: GitHub_M
Reserved: 2026-06-01 22:03 UTC
Published: 2026-07-14 20:45 UTC
Last updated: 2026-07-14 20:45 UTC
Primary CWE: CWE-409
CWE-409: Improper Handling of Highly Compressed Data (Data A…
Vendor / Product: tornadoweb / tornado
Sources: cve.org · NVD

Severity & Metrics

7.5 HIGH CVSS 3.1

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products (1)

Vendor	Product	Platform	Versions
tornadoweb	tornado	—	< 6.5.6

Weakness (CWE)

CWE	Source	Description
CWE-409	cna	CWE-409: Improper Handling of Highly Compressed Data (Data Amplification)

CVSS scores (1)

Score	Severity	Version	Source	Vector
7.5	HIGH	3.1	cna	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References (3)

https://github.com/tornadoweb/tornado/security/advisories/GHSA-mgf9-4vpg-hj56 https://github.com/tornadoweb/tornado/security/advisories/GHSA-mgf9-4vpg-hj56
https://github.com/tornadoweb/tornado/pull/3626 https://github.com/tornadoweb/tornado/pull/3626
https://github.com/tornadoweb/tornado/commit/ff808b33adc52d89a549376a5e3628e92abbc8ff https://github.com/tornadoweb/tornado/commit/ff808b33adc52d89a549376a5e3628e92abbc8ff