# CVE-2026-49854

## Summary

- **CVE ID:** CVE-2026-49854
- **Severity:** MEDIUM
- **CVSS Score:** 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N)
- **CWE:** CWE-126
- **Published:** Jul 14, 2026
- **Last Modified:** Jul 15, 2026

## Description

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.

## Affected Products

- tornadoweb — tornado (< 6.5.6)

## References

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

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.34%
- **EPSS Percentile:** 26.8

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._