Ubuntu update for nltk

Published: 2025-03-24

Risk	Medium
Patch available	YES
Number of vulnerabilities	2
CVE-ID	CVE-2021-3842 CVE-2021-43854
CWE-ID	CWE-1333
Exploitation vector	Network
Public exploit	N/A
Vulnerable software	Ubuntu Operating systems & Components / Operating system python-nltk (Ubuntu package) Operating systems & Components / Operating system package or component python3-nltk (Ubuntu package) Operating systems & Components / Operating system package or component
Vendor	Canonical Ltd.

Security Bulletin

This security bulletin contains information about 2 vulnerabilities.

1) Inefficient regular expression complexity

EUVDB-ID: #VU105951

Risk: Medium

CVSSv4.0: 6.6 [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-2021-3842

CWE-ID: CWE-1333 - Inefficient Regular Expression Complexity

Exploit availability: No

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.

Mitigation

Update the affected package nltk to the latest version.

Vulnerable software versions

Ubuntu: 14.04 - 20.04

python-nltk (Ubuntu package): before Ubuntu Pro

python3-nltk (Ubuntu package): before Ubuntu Pro

CPE2.3

External links

https://ubuntu.com/security/notices/USN-7365-1

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.

2) Inefficient regular expression complexity

EUVDB-ID: #VU105952