CVE-2026-49854 (CVSS 5.3)

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.

Is your site exposed to CVE-2026-49854?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

5.3

MEDIUM

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

EPSS — Exploit Prediction

0.0045

Probability of exploitation

0.36%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-126 CWE-126

References

Other 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

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-49854? +

CVE-2026-49854 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0045, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-49854? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2024-12975

A buffer overread can occur in the CPC application when operating in full duplex SPI upon receiving an invalid packet …

CVE-2026-41898 9.8

rust-openssl provides OpenSSL bindings for the Rust programming language. From 0.9.24 to before 0.10.78, the FFI trampolines behind SslContextBuilder::set_psk_client_callback, set_psk_server_callback, …

CVE-2017-17772 9.8

In multiple functions that process 802.11 frames, out-of-bounds reads can occur due to insufficient validation.

CVE-2024-38373 9.6

FreeRTOS-Plus-TCP is a lightweight TCP/IP stack for FreeRTOS. FreeRTOS-Plus-TCP versions 4.0.0 through 4.1.0 contain a buffer over-read issue in the …

CVE-2023-51773 9.1

BACnet Stack before 1.3.2 has a decode function APDU buffer over-read in bacapp_decode_application_data in bacapp.c.

CVE-2025-55081 9.1

In Eclipse Foundation NextX Duo before 6.4.4, a module of ThreadX, the _nx_secure_tls_process_clienthello() function was missing length verification of certain …

CVE-2026-49854