CVE-2026-49854

Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.6, the optional native extension tornado.speedups implemented websocket_mask without validating that the mask argument is exactly four bytes, allowing the C function to read up to three bytes beyond the provided buffer when reached through Tornado XSRF token decoding with the native extension active. This issue is fixed in version 6.5.6.

CVSS 3.1

5.3CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

EPSS

0.4% chance of exploitation in the next 30 days; higher than 35% of CVEs (scores of 2026-10-25)

CWE

CWE-126

Published

2026-07-14

Modified

2026-10-24

Record from

the NVD, synced 2026-10-25

Packages (OSV)

References

• https://github.com/tornadoweb/tornado/commit/96dc88c2a05705287856b2cd6b4b4034f9a6aaac
• https://github.com/tornadoweb/tornado/pull/3626
• https://github.com/tornadoweb/tornado/releases/tag/v6.5.6
• https://github.com/tornadoweb/tornado/security/advisories/GHSA-cx3h-4qpv-8hc9

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