Answer in brief
CVE-2026-12261 records a Medium severity (CVSS 6.5) vulnerability in Improper Access Control in nltk/nltk. The current sources do not mark it as known exploited. The current feed maps nltk/nltk/nltk (generic), nltk (pip), nltk (pypi). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 6.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps nltk/nltk/nltk (generic), nltk (pip), nltk (pypi). Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| nltk/nltk/nltkgeneric | unspecified | Not reported |
| nltkpip | <3.10.0 | 3.10.0 |
| nltkpypi | >=0 <3.10.0 | 3.10.0 |
Published upstream
Aug 7, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 23, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 7, 2026
A vulnerability in `nltk.downloader` in nltk/nltk versions <= 3.9.4 allows for cross-package resource and model poisoning. The downloader extracts package archives into shared namespaces such as `corpora/` and `taggers/` instead of package-isolated roots, and validates package integrity only after the archive has been written and extracted. This design flaw enables one package to overwrite another package's trusted resources within the same namespace, making the changes immediately active through ordinary NLTK APIs. This issue persists across fresh interpreter restarts and can affect downstream workflows, including machine learning pipelines and reproducibility-sensitive environments.
Quoted source text, attributed separately from HOL analysis.