CVE-2026-78681
NLTK before 3.10.3 Entity Expansion DoS via ElementTree
- State
- Published
- Severity
- 8.7 High
- Published
- Aug 25, 2026
- Updated
- Aug 26, 2026
- Reserved
- Aug 25, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.7 High | 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 | VulnCheck |
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | VulnCheck |
Weaknesses
- CWE-776 Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')
Affected Products
| Product | Versions |
|---|---|
nltknltk |
|
References
- GitHub Security Advisory (GHSA-97qj-x29f-37w7)vendor-advisory
- VulnCheck Advisory: NLTK before 3.10.3 Entity Expansion DoS via ElementTreethird-party-advisory
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