Description
NLTK versions before 3.10.3 contain a remote code execution vulnerability in allowlisted pickle loaders that trust entire module namespaces instead of specific safe callables. Attackers can craft malicious pickle payloads invoking dangerous in-namespace functions like ReppTokenizer._execute and numpy.f2py.crackfortran.myeval through pickle REDUCE to execute arbitrary commands during model or tokenizer artifact loading.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| nltk | nltk | < 3.10.3 | 3.10.3 |
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 | 3.10.3-1 | — |
| 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 | — |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
GitHub 1 repository
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federiconbaez/cortex9-nltk-pickle-allowlist-prefix-model ★ 0 · Nov 9, 2026
Offline educational model of CVE-2026-79657 (NLTK pickle allowlist prefix / gadget names)
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| PyPI | nltk | < 3.10.3 | 3.10.3 | GHSA-x99w-6fgc-pmfw |
References
- GitHub Security Advisory (GHSA-x99w-6fgc-pmfw) vendor-advisory
- VulnCheck Advisory: NLTK before 3.10.3 Remote Code Execution via Unsafe Pickle Deserialization third-party-advisory