# CVE-2026-78681

## Summary

- **CVE ID:** CVE-2026-78681
- **Severity:** HIGH
- **CVSS Score:** 8.7 (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)
- **CWE:** CWE-776
- **Published:** Aug 25, 2026
- **Last Modified:** Aug 26, 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.

## Affected Products

- nltk — nltk (0)
- nltk — nltk (3.10.3)

## References

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

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.29%
- **EPSS Percentile:** 21.8

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._