Inefficient regular expression complexity in Natural Language Toolkit - CVE-2021-43854
Published: March 24, 2025
Vulnerability identifier: #VU105952
CSH Severity: Medium
CVSS v4.0: 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/E:U/U:Green
CVE-ID: CVE-2021-43854
CWE-ID: CWE-1333
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: nltk.org
Affected software:
Natural Language Toolkit
Natural Language Toolkit
Detailed vulnerability description
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to insufficient input validation when processing untrusted input with a regular expressions. A remote attacker can pass specially crafted data to the application and perform regular expression denial of service (ReDos) attack.
How to mitigate CVE-2021-43854
Install update from vendor's website.