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CVE-2026-63310— NLTK before 3.9.3 Missing Post-Download Integrity Verification

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 版本在 3.9.3 之前，其下载器模块在从网络下载软件包后、解压前，未对文件完整性进行验证。攻击者可借此实施中间人攻击（Man-in-the-Middle, MitM）或 DNS 投毒（DNS Poisoning），注入恶意的软件包内容，而这些内容在解压时未经过任何验证即可被执行或部署。

CVSS 7.1 · High EPSS 0.15% · P5

Affected Version Matrix 2

VendorProduct Version RangeStatus
nltk nltk < 3.9.3 affected
3.9.3 unaffected
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I. Basic Information for CVE-2026-63310

Vulnerability Information
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Vulnerability Title
NLTK before 3.9.3 Missing Post-Download Integrity Verification
Source: CVE Program / CVE List V5
Vulnerability Description
NLTK before 3.9.3 fails to verify file integrity after downloading packages and before extraction in the downloader module. Attackers can perform man-in-the-middle attacks or DNS poisoning to inject malicious package contents that are extracted without validation.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
下载代码缺少完整性检查
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
nltk nltk 0 ~ 3.9.3 -

II. Public POCs for CVE-2026-63310

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Reproduced successfully in a real sandbox · Below is the actual recording of building the environment and exploiting the vulnerability.
Reproduction recording is a Pro+ exclusive
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claude_code · 10325 chars
Pro+ exclusive includes:
Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
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100+ AI POC generations per month

III. Intelligence Information for CVE-2026-63310

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Vendor Advisories for CVE-2026-63310 (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-2026-65915 6.5 MEDIUM NLTK before 3.10.0 Arbitrary File Read via FileSystemPathPointer
CVE-2026-70626 6.2 MEDIUM NLTK before 3.9.4 Symlink Escape via CorpusReader
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-494

V. Comments for CVE-2026-63310

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