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CVE-2026-70626— NLTK before 3.9.4 Symlink Escape via CorpusReader

Quick assessment

Affected
nltk nltk
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

NLTK 3.9.4 之前的版本在 CorpusReader.open() 方法中存在符号链接绕过漏洞，允许本地攻击者读取语料库根目录之外的任意文件。该漏洞的成因在于路径验证仅基于 lexical（词法）比较，未考虑符号链接的实际解析过程。攻击者通过在语料库根目录内放置符号链接，可突破预期边界，访问受限目录外的文件。 （注：lexical path validation 指仅通过字符串比较验证路径，而未使用 realpath 等系统调用解析符号链接的实际路径；symlink escape 指利用符号链接特性绕过基于

CVSS 6.2 · Medium EPSS 0.14% · P4

Possible ATT&CK Techniques 1 AI

T1083 · File and Directory Discovery

Affected Version Matrix 2

VendorProduct Version RangeStatus
nltk nltk < 3.9.4 affected
3.9.4 unaffected
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I. Basic Information for CVE-2026-70626

Vulnerability Information
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Vulnerability Title
NLTK before 3.9.4 Symlink Escape via CorpusReader
Source: CVE Program / CVE List V5
Vulnerability Description
NLTK versions before 3.9.4 contain a symlink escape vulnerability in CorpusReader.open() that allows local attackers to read arbitrary files outside the corpus root. The vulnerability exists because path validation is lexical and does not account for symlink resolution, enabling attackers to place symlinks inside the corpus root to access files outside the intended boundary.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在文件访问前对链接解析不恰当(链接跟随)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
nltk nltk 0 ~ 3.9.4 -

II. Public POCs for CVE-2026-70626

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III. Intelligence Information for CVE-2026-70626

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Vendor Advisories for CVE-2026-70626 (2)

Same Patch Batch · nltk · 2026-08-22 · 12 CVEs total

CVE-2026-71513 8.8 HIGH NLTK 3.10.0 through 3.10.2 Remote Code Execution via AllowlistUnpickler Dotted-Name Bypass
CVE-2026-62388 7.5 HIGH NLTK before 3.10.0 Insecure Default Configuration pathsec
CVE-2026-62384 7.5 HIGH NLTK FramenetCorpusReader Symlink Sandbox Bypass before 3.10.2
CVE-2026-66393 7.5 HIGH NLTK before 3.9.4 Denial of Service via JSONTaggedDecoder
CVE-2026-63312 7.5 HIGH NLTK StreamBackedCorpusView Bypasses pathsec.ENFORCE Arbitrary File Read
CVE-2026-63310 7.1 HIGH NLTK before 3.9.3 Missing Post-Download Integrity Verification
CVE-2026-65915 6.5 MEDIUM NLTK before 3.10.0 Arbitrary File Read via FileSystemPathPointer
CVE-2026-62385 5.9 MEDIUM NLTK 3.9.4 Path Traversal via FrameNet and NKJP Readers
CVE-2026-62383 5.5 MEDIUM nltk IPIPANCorpusReader Symlink Arbitrary File Read
CVE-2026-63311 5.3 MEDIUM NLTK before 3.10.0 SSRF via DNS Resolution Failure
CVE-2026-71514 2.5 LOW NLTK 3.9.4 through 3.10.2 Path Traversal via CrubadanCorpusReader pathsec Bypass

IV. Related Vulnerabilities

Same product: nltk
Same vendor: nltk
Same weakness: CWE-59

V. Comments for CVE-2026-70626

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