Answer in brief
CVE-2026-12259 records a Medium severity (CVSS 7.1) vulnerability in NLTK before 3.9.3 Missing Post-Download Integrity Verification. The current sources do not mark it as known exploited. The current feed maps nltk/nltk (generic), 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 7.1. 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 (generic), 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/nltkgeneric | >=0 <3.9.3 | 3.9.3 |
| nltk/nltk/nltkgeneric | unspecified | Not reported |
| nltkpip | <=3.9.2 | 3.9.3 |
| nltkpypi | >=0 <3.9.3 | 3.9.3 |
Published upstream
Aug 22, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 8, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 22, 2026
NLTK before 3.9.3 fails to verify file integrity after downloading packages and before extraction in the downloader module. Attackers can perform man-in-the-middle attacks or DNS poisoning to inject malicious package contents that are extracted without validation.
Quoted source text, attributed separately from HOL analysis.