CVE-2026-71513
NLTK 3.10.0 through 3.10.2 Remote Code Execution via AllowlistUnpickler Dotted-Name Bypass
Description
NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load.
INFO
Published Date :
Aug. 22, 2026, 2:16 p.m.
Last Modified :
Oct. 14, 2026, 7:10 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 | HIGH | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | HIGH | MITRE-CVE | ||||
| CVSS 4.0 | HIGH | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 4.0 | HIGH | [email protected] |
Solution
- Update NLTK to version 3.10.3 or later.
- Avoid loading untrusted transition-parser models.
- Validate pickle data sources carefully.
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-2026-71513.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-71513 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-2026-71513
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-2026-71513 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-71513 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.
-
CVE Translated by [email protected]
Oct. 14, 2026
Action Type Old Value New Value Added Translation Title: nltk, Description: NLTK anterior a la versión 3.10.3 contiene una vulnerabilidad de ejecución remota de código en AllowlistUnpickler que valida solo la cadena del módulo pickle y no el nombre global, permitiendo a los atacantes resolver nombres con puntos mediante la transversalidad de atributos a elementos invocables fuera del espacio de nombres en la lista blanca. Los atacantes pueden crear modelos de analizador de transición no confiables que ejecutan comandos arbitrarios cuando TransitionParser.parse carga el modelo a través de allowlisted_pickle_load. -
Initial Analysis by [email protected]
Sep. 16, 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 Types: Product Added Reference Type VulnCheck: https://github.com/nltk/nltk/blob/v3.10.2/nltk/picklesec.py#L119-L124 Types: Product Added Reference Type VulnCheck: https://github.com/nltk/nltk/commit/c3e37113742a1ebeeb4f2ca58941f320f98805ea Types: Patch Added Reference Type VulnCheck: https://www.vulncheck.com/advisories/nltk-through-remote-code-execution-via-allowlistunpickler-dotted-name-bypass Types: Patch, Third Party Advisory -
CVE Modified by [email protected]
Aug. 27, 2026
Action Type Old Value New Value Added Reference https://github.com/nltk/nltk Added Reference https://github.com/nltk/nltk/blob/v3.10.2/nltk/picklesec.py#L119-L124 Added Reference https://github.com/nltk/nltk/commit/c3e37113742a1ebeeb4f2ca58941f320f98805ea Added Reference https://www.vulncheck.com/advisories/nltk-through-remote-code-execution-via-allowlistunpickler-dotted-name-bypass Removed Reference https://github.com/nltk/nltk Removed Reference https://github.com/nltk/nltk/blob/v3.10.2/nltk/picklesec.py#L119-L124 Removed Reference https://github.com/nltk/nltk/commit/c3e37113742a1ebeeb4f2ca58941f320f98805ea Removed Reference https://www.vulncheck.com/advisories/nltk-through-remote-code-execution-via-allowlistunpickler-dotted-name-bypass -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 27, 2026
Action Type Old Value New Value Changed SSVC {'id': 'CVE-2026-71513', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-08-24T00:00:00+00:00'} {'id': 'CVE-2026-71513', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-08-25T03:56:57.129387Z'} -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 25, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-71513', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-08-24T00:00:00+00:00'} -
New CVE Received by [email protected]
Aug. 22, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'nltk', 'product': 'nltk', 'versions': [{'status': 'affected', 'version': '3.10.0', 'lessThan': '3.10.3', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '3.10.3', 'versionType': 'semver'}], 'packageURL': 'pkg:pypi/nltk', 'defaultStatus': 'unaffected'}] Added Description NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:P/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:R/S:U/C:H/I:H/A:H Added CWE CWE-502 Added Reference https://github.com/nltk/nltk Added Reference https://github.com/nltk/nltk/blob/v3.10.2/nltk/picklesec.py#L119-L124 Added Reference https://github.com/nltk/nltk/commit/c3e37113742a1ebeeb4f2ca58941f320f98805ea Added Reference https://www.vulncheck.com/advisories/nltk-through-remote-code-execution-via-allowlistunpickler-dotted-name-bypass