CVE-2026-81725

Severity CVSS v4.0:

MEDIUM

Type:

CWE-400 Uncontrolled Resource Consumption ('Resource Exhaustion')

Publication date:

27/08/2026

Last modified:

28/08/2026

Description

NLTK before 3.10.3 contains a regular expression denial of service vulnerability in Pl196xCorpusReader that allows attackers to cause quadratic CPU consumption by supplying malformed TEI blocks with many unmatched opening tags. Attackers can exploit lazy regex patterns in the read_block method through public APIs like words() and tagged_words() to force repeated rescans and achieve near-quadratic runtime growth.

Impact

Vector 4.0

CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N CVSS v4.0 Severity and Metrics:

Base Score: 6.30 MEDIUM
Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

Attack Vector (AV): Network
Attack Complexity (AC): High
Attack Requirements (AT): Present
Privileges Required (PR): None
User Interaction (UI): None
Confidentiality (VC): None
Integrity (VI): None
Availability (VA): Low
Confidentiality (SC): None
Integrity (SI): None
Availability (SA): None

Base Score 4.0

6.30

Severity 4.0

MEDIUM

Vector 3.x

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L CVSS v3.1 Severity and Metrics:

Base Score: 3.70 LOW
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector (AV): Network
Attack Complexity (AC): High
Privileges Required (PR): None
User Interaction (UI): None
Scope (S): Unchanged
Confidentiality (C): None
Integrity (I): None
Availability (A): Low

Base Score 3.x

3.70

Severity 3.x

LOW

CVE-2026-81725

Description

Impact

References to Advisories, Solutions, and Tools