CVE-2026-78681

EUVD-2026-65227
NLTK versions before 3.10.3 use xml.etree.ElementTree to parse XML in multiple modules, which honors entity declarations in document DTDs. Attackers can craft XML payloads with nested entity declarations that expand from hundreds of bytes to megabytes in memory, causing denial of service.
XML Entity Expansion
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
VulnCheckCNA
7.5 HIGH
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Base Score
CVSS 3.x
EPSS Score
Percentile: 19.76%
Early Detection
Affected products identified ahead of NVD analysis through intelligence sources.
VendorProductVersionSource
nltknltk
𝑥
< 3.10.3
CNA
Common Weakness Enumeration
References
https://github.com/nltk/nltk/security/advisories/GHSA-97qj-x29f-37w7
https://www.vulncheck.com/advisories/nltk-before-entity-expansion-dos-via-elementtree