6.3

CVE-2026-81725: nltk Uncontrolled Resource Consumption

CVSS: 6.3v4.0MediumAnalyzed
AliasesGHSA-8mpw-7fpc-4gqjPYSEC-2026-3752UBUNTU-CVE-2026-81725
Published 27-08-2026Last modified 28-08-2026
Open JSON

Vulnerability summary

CVE-2026-81725 is a medium (CVSS 6.3) Uncontrolled Resource Consumption vulnerability in nltk. EPSS estimates a 0.37% chance of exploitation in the next 30 days, higher than 29.3% of scored vulnerabilities. 1 public exploit is recorded.

Overall risk
35/100
0100
Medium · default modelHow is this calculated?
CVSS score
6.3/10
010
Medium · v4.0 (CVE.org)
EPSS score
0.37%
0%100%
Low · +0.14 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits1github

Timeline

  1. 27-08-2026
    PublishedVulnerability first disclosed.
  2. 28-08-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

8 scores · 5 sources · 2 versions

EPSS trend

Probability

0.37%

Chance of exploitation in the next 30 days

Percentile

29%

Versus all other CVEs

30-day change

+0.14 pp

From 0.23% on 20-09-2026

20-09-202620-10-2026
EPSS score
0.37%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

1 found
  • githubUnverified

    Nltk

    Maturity: poc

Weaknesses

CWE · root cause

Affected systems

Debian1 product
  • nltkAll versions (No fix recorded) | < 3.10.3-1
Nltk1 product
PyPI1 product
  • nltk< 3.10.3
Ubuntu1 product
  • nltkAll versions (No fix recorded)

4 vendors · 4 products

References

10 links