Description
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 products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| nltk | nltk | < 3.9.4 | 3.9.4 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | nltk | 3.10.0-1 | — |
| Debian 13 | nltk | No fix yet | — |
| Debian 12 | nltk | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 26.04 LTS | nltk | No fix yet | — |
| Ubuntu Pro 24.04 LTS | nltk | No fix yet | — |
| Ubuntu Pro 22.04 LTS | nltk | No fix yet | — |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | nltk | No fix yet | — |
| Ubuntu Pro 18.04 LTS | nltk | No fix yet | — |
| Ubuntu Pro 16.04 LTS | nltk | No fix yet | — |
| Ubuntu Pro 14.04 LTS | nltk | No fix yet | — |
Wolfi
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Wolfi rolling | kubeflow-pipelines-visualization-server | 2.16.0-r3 | — |
| Wolfi rolling | open-webui | 0.8.12-r1 | — |
| Wolfi rolling | py3.11-nltk +2 | 3.9.4-r0 | — |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| PyPI | nltk | < 3.9.4 | 3.9.4 | GHSA-rf74-v2fm-23pw |
References
- GitHub Security Advisory (GHSA-rf74-v2fm-23pw) vendor-advisory
- VulnCheck Advisory: NLTK before 3.9.4 Denial of Service via JSONTaggedDecoder third-party-advisory