Path traversal in Tornado - CVE-2026-103263
Published: September 15, 2026 / Updated: October 1, 2026
Vulnerability identifier: #VU149942
CSH Severity: Medium
CVSS v4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-103263
CWE-ID: CWE-22
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to disclose sensitive information.
The vulnerability exists due to improper path validation in tornado.web.StaticFileHandler when handling requests for paths that resolve through symbolic links. A remote attacker can request a path to a symbolic link within the static root to disclose sensitive information.
Exploitation requires a symbolic link within the static root that points outside that root.
Affected software
Tornado
Ubuntu
python3-tornado (Ubuntu package)
Ubuntu
python3-tornado (Ubuntu package)
How to mitigate CVE-2026-103263
Install security update from vendor's website.
Tornado - update to 6.5.9
python3-tornado (Ubuntu package) - addressed in versions 4.2.1-1ubuntu3.1+esm4, 4.5.3-1ubuntu0.2+esm4, 6.0.3+really5.1.1-3ubuntu0.1~esm7, 6.1.0-3ubuntu0.1~esm6, 6.4.0-1ubuntu0.6, 6.5.4-0.1ubuntu0.2, 6.5.5-5ubuntu1.1
python3-tornado (Ubuntu package) - addressed in versions 4.2.1-1ubuntu3.1+esm4, 4.5.3-1ubuntu0.2+esm4, 6.0.3+really5.1.1-3ubuntu0.1~esm7, 6.1.0-3ubuntu0.1~esm6, 6.4.0-1ubuntu0.6, 6.5.4-0.1ubuntu0.2, 6.5.5-5ubuntu1.1