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CVE-2026-78682— NLTK before 3.10.3 SSRF Protection Bypass via Proxy

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 在 3.10.3 版本之前存在一个服务器端请求伪造（SSRF）漏洞，该漏洞位于 函数中（以及调用该函数的 、 等方法），前提是系统中配置了 HTTP 代理。虽然 会在本地对请求的主机名进行验证，但由于代理处理程序的继承机制禁用了安全的 HTTP/HTTPS 处理器，实际的数据获取请求由代理转发，而目标地址在代理层面不再进行任何验证。攻击者可以提供一个经本地验证的公共 URL，该 URL 被代理转发至仅允许内部回环地址访问的服务，从而导致内部 HTTP 资源的泄露、伪造的下载器索引文件的加载，以及攻击者自定

CVSS 7.5 · High EPSS 0.24% · P16

Affected Version Matrix 2

VendorProduct Version RangeStatus
nltk nltk < 3.10.3 affected
3.10.3 unaffected
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I. Basic Information for CVE-2026-78682

Vulnerability Information
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Vulnerability Title
NLTK before 3.10.3 SSRF Protection Bypass via Proxy
Source: CVE Program / CVE List V5
Vulnerability Description
NLTK before 3.10.3 contains a server-side request forgery vulnerability in nltk.pathsec.urlopen (and callers nltk.data.load, nltk.downloader.Downloader.index/download) when an HTTP proxy is configured. pathsec.urlopen validates the requested hostname locally, but proxy-handler inheritance disables the safe HTTP/HTTPS handlers so the actual fetch is performed by the proxy against a destination that is never re-validated. An attacker can supply a validated public URL that the proxy forwards to an internal loopback-only service, allowing disclosure of internal HTTP resources, loading of forged downloader indexes, and installation of attacker-chosen package content.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
服务端请求伪造(SSRF)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
nltk nltk 0 ~ 3.10.3 -

II. Public POCs for CVE-2026-78682

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 11164 chars
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III. Intelligence Information for CVE-2026-78682

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Vendor Advisories for CVE-2026-78682 (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-2026-78683 9.6 CRITICAL NLTK before 3.10.0 Remote Code Execution via Unsafe Pickle Deserialization
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-2026-79676 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-918

V. Comments for CVE-2026-78682

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