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CVE-2026-78683— NLTK before 3.10.0 Remote Code Execution via Unsafe Pickle Deserialization

Quick assessment

Affected
nltk nltk
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

NLTK 3.10.0 之前版本（受影响版本为 <=3.9.4）在 TransitionParser.parse() 方法（位于 nltk/parse/transitionparser.py）中存在不安全的 pickle 反序列化漏洞。该方法调用 pickle_load() 时使用了默认的 restricted=False 参数，将反序列化过程路由至 WarningUnpickler，而该类并未重写 find_class() 方法，因此允许任意类解析。当应用程序加载攻击者构造的模型文件时，内嵌的 pickle ga

CVSS 9.6 · Critical EPSS 0.28% · P19

Possible ATT&CK Techniques 1 AI

T1210 · Exploitation of Remote Services

Affected Version Matrix 2

VendorProduct Version RangeStatus
nltk nltk < 3.10.0 affected
3.10.0 unaffected
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I. Basic Information for CVE-2026-78683

Vulnerability Information
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Vulnerability Title
NLTK before 3.10.0 Remote Code Execution via Unsafe Pickle Deserialization
Source: CVE Program / CVE List V5
Vulnerability Description
NLTK before 3.10.0 (affected versions <=3.9.4) contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse() method (nltk/parse/transitionparser.py). The method calls pickle_load() with the default restricted=False, routing deserialization through WarningUnpickler, which does not override find_class() and therefore permits arbitrary class resolution. When an application loads an attacker-crafted model file, embedded pickle gadget chains execute arbitrary Python code with the privileges of the user running the application. NLTK provides a RestrictedUnpickler for safe deserialization, but it is not used by production code paths. Fixed in 3.10.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
可信数据的反序列化
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
nltk nltk 0 ~ 3.10.0 -

II. Public POCs for CVE-2026-78683

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Qwen3.6-35B-A3B · 7790 chars
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III. Intelligence Information for CVE-2026-78683

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Vendor Advisories for CVE-2026-78683 (2)

Same Patch Batch · nltk · 2026-08-25 · 8 CVEs total

CVE-2026-79657 9.8 CRITICAL NLTK before 3.10.3 Remote Code Execution via Unsafe Pickle Deserialization
CVE-2026-79675 9.8 CRITICAL NLTK before 3.10.3 JVM Argument Injection via Per-Call Options
CVE-2026-79674 8.2 HIGH NLTK 3.10.2 Path Traversal via corpus-reader constructors
CVE-2026-78680 7.8 HIGH NLTK before 3.10.3 Arbitrary Code Execution via Graphviz dot Binary
CVE-2026-78681 7.5 HIGH NLTK before 3.10.3 Entity Expansion DoS via ElementTree
CVE-2026-78682 7.5 HIGH NLTK before 3.10.3 SSRF Protection Bypass via Proxy
CVE-2026-79676 5.9 MEDIUM NLTK before 3.10.3 Path Traversal via Symlink Bypass

IV. Related Vulnerabilities

Same product: nltk
Same vendor: nltk
Same weakness: CWE-502

V. Comments for CVE-2026-78683

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