Untrusted JAR Code Execution in Multiple Stanford Interface Classes in nltk/nltk
Key facts
- Attack vector
- Local
- Privileges required
- None
- User interaction
- Required
- Attack complexity
- Low
- Impact type
- Code execution
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Partial Red Hat: 1 without a fix
Attack profile from CVSS 3.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-94.
Summary
In nltk/nltk versions 3.9.3 and earlier, five Stanford interface classes (StanfordPOSTagger, StanfordNERTagger, StanfordParser, StanfordDependencyParser, and StanfordNeuralDependencyParser) are vulnerable to untrusted JAR code execution. These classes accept user-controllable JAR paths and execute them via the `java()` function, which invokes `subprocess.Popen()` without integrity verification. This vulnerability is identical to CVE-2026-0848, which was fixed for StanfordSegmenter by adding SHA256 verification. However, the fix was not applied to these additional classes, leaving them susceptible to arbitrary code execution when loading untrusted JAR files.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| nltk | nltk/nltk | up to latest | — | No fix listed | CNA |
| — | nltk (PyPI) | before 3.9.4 | 3.9.4 | Patch available | GHSA-9r6g-266r-89x4 |
- nltk/nltk Vendornltk Affected up to latest Fixed in — No fix listed CNA
- nltk (PyPI) Vendor— Affected before 3.9.4 Fixed in 3.9.4 Patch available GHSA-9r6g-266r-89x4
Remediation
- Fix · GHSA-9r6g-266r-89x4 nltk (PyPI) Fixed in 3.9.4 Advisory →
Vendor assessments
Red Hat
Red Hat rating: Important. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| OpenShift Lightspeed | Affected | No fix yet |
Not affected: 5 products
- Exploit Intelligence
- Lightspeed Core
- OpenShift Lightspeed
- Red Hat Ansible Automation Platform 2
- Red Hat OpenShift AI (RHOAI)
Timeline
- 2026-10-02 Threatist record created from CVE-2026-12252
- 2026-10-03 Alias added: GHSA-9r6g-266r-89x4
References
Other 6
- https://github.com/nltk/nltk/pull/3743
- https://github.com/nltk/nltk/commit/006f4b83d430147b067b81e2cddd226d6fa405c8
- https://github.com/nltk/nltk/commit/24777f0cb8c33ed2839d16e0f8169a3c312a6806
- https://github.com/nltk/nltk
- https://github.com/nltk/nltk/releases/tag/v3.10.3
- https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-2085.yaml
More Nltk vulnerabilities
- TI-2026-00629 Arbitrary Code Execution in NLTK StanfordSegmenter via Untrusted JAR Loading CVSS 3.0CRITICAL 10.0
- TI-2025-12800 Zip Slip Vulnerability in nltk/nltk Leading to Remote Code Execution CVSS 3.0CRITICAL 10.0
- TI-2026-55173 NLTK before 3.10.3 JVM Argument Injection via Per-Call Options CVSS 4.0CRITICAL 9.3
- TI-2026-55155 NLTK before 3.10.3 Remote Code Execution via Unsafe Pickle Deserialization CVSS 4.0CRITICAL 9.3
- TI-2026-56370 nltk PorterStemmer before 3.10.3 Quadratic-time DoS CVSS 4.0HIGH 8.7
- TI-2026-55172 NLTK 3.10.2 Path Traversal via corpus-reader constructors CVSS 4.0HIGH 8.8
Sources
- CVE-2026-12252 · CVE Program
- CVE-2026-12252 · NVD
- FIRST EPSS
- GHSA-9r6g-266r-89x4 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-12252 · Red Hat security data · CC BY 4.0
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