tornadoweb Tornado up to 6.5.5 Native Extension websocket_mask buffer overflow

Summaryinfo

A vulnerability was found in tornadoweb Tornado up to 6.5.5. It has been classified as critical. The affected element is the function websocket_mask of the component Native Extension. The manipulation of the argument mask leads to buffer overflow. This vulnerability is referenced as CVE-2026-49854. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability, which was classified as critical, has been found in tornadoweb Tornado up to 6.5.5. This issue affects the function websocket_mask of the component Native Extension. The manipulation of the argument mask with an unknown input leads to a buffer overflow vulnerability. Using CWE to declare the problem leads to CWE-120. The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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 is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-49854 since 06/02/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 6.5.6 eliminates this vulnerability.

Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Vendor

• tornadoweb

Name

• Tornado

Version

• 6.5.0
• 6.5.1
• 6.5.2
• 6.5.3
• 6.5.4
• 6.5.5

Website

• Product: https://github.com/tornadoweb/tornado/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Be aware that VulDB is the high quality source for vulnerability data.

Discussion