Buffer over-read in Tornado - CVE-2026-49854

Vulnerability identifier: #VU149934

CSH Severity: Medium

CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-49854

CWE-ID: CWE-126

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to disclose sensitive information.

The vulnerability exists due to a buffer over-read in the tornado.speedups websocket_mask function when processing XSRF tokens. A remote attacker can send a crafted XSRF token with a short mask to disclose sensitive information.

The issue is reachable when xsrf_cookies is enabled and the native extension is active.

Tornado
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Desktop 12
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Micro
SUSE Linux Enterprise Micro for Rancher
SUSE Manager Client Tools for SLE
SUSE Linux Enterprise Server for the Raspberry Pi
SUSE Linux Enterprise Server
SUSE Linux Enterprise Server for SAP Applications
SUSE Linux Enterprise Desktop
Basesystem Module
Python 3 Module
openSUSE Leap
openEuler
python3-tornado
python-tornado
python-tornado-debuginfo
python-tornado-debugsource
python3-tornado-debuginfo
python311-tornado6-debuginfo
python311-tornado6
python-tornado6-debugsource
python-tornado-help

Install security update from vendor's website.

Tornado - update to 6.5.6
python3-tornado - addressed in versions 4.2.1-17.21.1, 4.5.3-150000.3.22.1
python-tornado - update to 4.2.1-17.21.1
python-tornado-debuginfo - addressed in versions 4.2.1-17.21.1, 4.5.3-150000.3.22.1
python-tornado-debugsource - addressed in versions 4.2.1-17.21.1, 4.5.3-150000.3.22.1
python3-tornado-debuginfo - update to 4.5.3-150000.3.22.1
python311-tornado6-debuginfo - update to 6.3.2-150400.9.18.1
python311-tornado6 - update to 6.3.2-150400.9.18.1
python-tornado6-debugsource - update to 6.3.2-150400.9.18.1
python-tornado - update to 6.5-5
python3-tornado - update to 6.5-5
python-tornado-help - update to 6.5-5
python-tornado-debugsource - update to 6.5-5
python-tornado-debuginfo - update to 6.5-5

• https://github.com/tornadoweb/tornado/security/advisories/GHSA-cx3h-4qpv-8hc9

• Multiple vulnerabilities in Tornado
• openEuler 24.03 LTS SP3 update for python-tornado
• openEuler 24.03 LTS SP1 update for python-tornado
• SUSE update for python-tornado6
• SUSE update for python-tornado
• SUSE update for python-tornado