Improper Validation of Specified Quantity in Input in Tornado - CVE-2026-82397

Vulnerability identifier: #VU149939

CSH Severity: Medium

CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-82397

CWE-ID: CWE-1284

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to improper validation of the number of fields in application/x-www-form-urlencoded body parsing when processing a crafted form request containing numerous separators. A remote attacker can send a specially crafted form request to cause a denial of service.

The synchronous parsing occurs on the event loop before request dispatch, causing other connections to wait.

Tornado
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Micro for Rancher
SUSE Linux Enterprise Micro
Python 3 Module
Basesystem Module
openSUSE Leap
python-tornado-debuginfo
python3-tornado
python-tornado-debugsource
python3-tornado-debuginfo
python311-tornado6-debuginfo
python311-tornado6
python-tornado6-debugsource

Install security update from vendor's website.

Tornado - update to 6.5.8
python-tornado-debuginfo - update to 4.5.3-150000.3.28.1
python3-tornado - update to 4.5.3-150000.3.28.1
python-tornado-debugsource - update to 4.5.3-150000.3.28.1
python3-tornado-debuginfo - update to 4.5.3-150000.3.28.1
python311-tornado6-debuginfo - update to 6.3.2-150400.9.24.1
python311-tornado6 - update to 6.3.2-150400.9.24.1
python-tornado6-debugsource - update to 6.3.2-150400.9.24.1

• https://github.com/tornadoweb/tornado/security/advisories/GHSA-mpf4-983q-p7j4

• Multiple vulnerabilities in Tornado
• SUSE update for python-tornado
• SUSE update for python-tornado6