CVE-2026-78681

Description

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.

CVSS Vector

References

• https://github.com/nltk/nltk/security/advisories/GHSA-97qj-x29f-37w7
• https://www.vulncheck.com/advisories/nltk-before-entity-expansion-dos-via-elementtree