Uncontrolled Recursion in Natural Language Toolkit - CVE-2026-66393
Published: March 18, 2026 / Updated: September 14, 2026
Vulnerability identifier: #VU124091
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-66393
CWE-ID: CWE-674
Exploitation vector: Remote access
Exploit availability:
Public exploit is available
Vulnerability details
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to uncontrolled recursion in JSONTaggedDecoder.decode_obj(). A remote attacker can pass specially crafted input to the application and perform a denial of service (DoS) attack.
Affected software
Natural Language Toolkit
How to mitigate CVE-2026-66393
Install update from vendor's website.
Natural Language Toolkit - update to 3.9.4