CVE-2026-49854 (Low) detected in tornado-5.1.1.tar.gz

[mend-bolt-for-github]

CVE-2026-49854 - Low Severity Vulnerability

Vulnerable Library - tornado-5.1.1.tar.gz

Tornado is a Python web framework and asynchronous networking library, originally developed at FriendFeed.

Library home page: https://files.pythonhosted.org/packages/e6/78/6e7b5af12c12bdf38ca9bfe863fcaf53dc10430a312d0324e76c1e5ca426/tornado-5.1.1.tar.gz

Path to dependency file: /tmp/ws-ua_20220122232947_MZFNWS/archiveExtraction_KXRZMM/PZSZKX/20220122232947/codechung_depth_0/awscli-bundle/packages/urllib3-1.25.10.tar/urllib3-1.25.10/dev-requirements.txt

Path to vulnerable library: /awscli-bundle/packages/urllib3-1.25.10.tar/urllib3-1.25.10/dev-requirements.txt,/awscli-bundle/awscli-bundle/packages/urllib3-1.25.7.tar/urllib3-1.25.7/dev-requirements.txt,/awscli-bundle/awscli-bundle/packages/urllib3-1.25.10.tar/urllib3-1.25.10/dev-requirements.txt,/awscli-bundle/awscli-bundle/packages/urllib3-1.25.7.tar/urllib3-1.25.7/docs/requirements.txt,/awscli-bundle/packages/urllib3-1.25.10.tar/urllib3-1.25.10/docs/requirements.txt,/awscli-bundle/packages/urllib3-1.25.7.tar/urllib3-1.25.7/docs/requirements.txt,/awscli-bundle/awscli-bundle/packages/urllib3-1.25.10.tar/urllib3-1.25.10/docs/requirements.txt,/awscli-bundle/packages/urllib3-1.25.7.tar/urllib3-1.25.7/dev-requirements.txt

Dependency Hierarchy:

• ❌ tornado-5.1.1.tar.gz (Vulnerable Library)

Found in HEAD commit: de1c2b0d1a23367b161c2d995029f9693bd8a155

Found in base branch: master

Vulnerability Details

Summary Tornado's optional native extension "tornado.speedups" implements "websocket_mask" without validating that the "mask" argument is exactly four bytes long. The C function reads four bytes from "mask" unconditionally, even when Python passes a shorter byte string. This can read beyond the provided buffer, exposing up to 3 bytes of uninitialized memory. The behavior is reachable from Tornado's XSRF token decoder when "xsrf_cookies=True" and the native extension is active. Mitigations This bug is fixed in Tornado 6.5.6. Prior to upgrading to this version, setting the environment variable TORNADO_EXTENSION=0 will disable the vulnerable code (at the expense of reducing websocket performance).

Publish Date: 2026-06-13

URL: CVE-2026-49854

CVSS 3 Score Details (3.7)

Base Score Metrics:

• Exploitability Metrics:
  • Attack Vector: Network
  • Attack Complexity: High
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
• Impact Metrics:
  • Confidentiality Impact: Low
  • Integrity Impact: None
  • Availability Impact: None

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Origin: GHSA-cx3h-4qpv-8hc9

Release Date: 2026-06-13

Fix Resolution: 6.5.6

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