CVE-2026-79657
NLTK before 3.10.3 Remote Code Execution via Unsafe Pickle Deserialization
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.
INFO
Published Date :
Aug. 25, 2026, 12:16 p.m.
Last Modified :
Aug. 31, 2026, 7:05 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | CRITICAL | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 3.1 | CRITICAL | [email protected] | ||||
| CVSS 3.1 | CRITICAL | MITRE-CVE | ||||
| CVSS 4.0 | CRITICAL | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 4.0 | CRITICAL | [email protected] |
Solution
- Update NLTK to version 3.10.3 or later.
- Avoid loading untrusted pickle data.
- Restrict access to model loading functions.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-79657.
| URL | Resource |
|---|---|
| https://github.com/nltk/nltk/security/advisories/GHSA-x99w-6fgc-pmfw | Exploit Vendor Advisory |
| https://www.vulncheck.com/advisories/nltk-before-3.10.3-remote-code-execution-via-unsafe-pickle-deserialization | Third Party Advisory |
| https://github.com/nltk/nltk/security/advisories/GHSA-x99w-6fgc-pmfw | Exploit Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-79657 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-79657
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-79657 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-79657 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Aug. 31, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:* versions up to (excluding) 3.10.3 Added Reference Type VulnCheck: https://github.com/nltk/nltk/security/advisories/GHSA-x99w-6fgc-pmfw Types: Exploit, Vendor Advisory Added Reference Type VulnCheck: https://www.vulncheck.com/advisories/nltk-before-3.10.3-remote-code-execution-via-unsafe-pickle-deserialization Types: Third Party Advisory Added Reference Type CISA-ADP: https://github.com/nltk/nltk/security/advisories/GHSA-x99w-6fgc-pmfw Types: Exploit, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 25, 2026
Action Type Old Value New Value Added Reference https://github.com/nltk/nltk/security/advisories/GHSA-x99w-6fgc-pmfw Added SSVC {'id': 'CVE-2026-79657', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'yes'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-08-25T15:58:28.455681Z'} -
New CVE Received by [email protected]
Aug. 25, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'nltk', 'product': 'nltk', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': '3.10.3', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '3.10.3', 'versionType': 'semver'}], 'defaultStatus': 'unaffected'}] Added 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. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Added CWE CWE-502 Added Reference https://github.com/nltk/nltk/security/advisories/GHSA-x99w-6fgc-pmfw Added Reference https://www.vulncheck.com/advisories/nltk-before-3.10.3-remote-code-execution-via-unsafe-pickle-deserialization