high7.5
CVE-2026-66393
NLTK versions before 3.9.4 contain an unbounded recursion vulnerability in JSONTaggedDecoder.decode_obj() that allows attackers to cause denial of service by s…
Impact
NLTK versions before 3.9.4 contain an unbounded recursion vulnerability in JSONTaggedDecoder.decode_obj() that allows attackers to cause denial of service by supplying deeply nested JSON structures. Attackers can craft JSON payloads exceeding the recursion limit to trigger an unhandled RecursionError that crashes the Python process.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | nltk | <= 3.9.3 | 3.9.4 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Nltk | Nltk | before 3.9.4 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-rf74-v2fm-23pw
- https://github.com/nltk/nltk/security/advisories/GHSA-rf74-v2fm-23pw
- https://nvd.nist.gov/vuln/detail/CVE-2026-66393
- https://github.com/nltk/nltk/commit/00cdcd392142e6c745e7120c8d50a24127df5fad
- https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3724.yaml
- https://www.vulncheck.com/advisories/nltk-before-denial-of-service-via-jsontaggeddecoder