EUVD-2026-64314
GHSA-8h9m-22mv-qv5r
Severity by source
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/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
Symlink placement requires corpus-directory write access (PR:L, AV:L); only file read is described, so I:N and A:N.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
Lifecycle Timeline
3Blast Radius
ecosystem impact- 184 pypi packages depend on nltk (42 direct, 142 indirect)
Ecosystem-wide dependent count for version 3.9.4.
DescriptionCVE.org
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.
AnalysisAI
Symlink escape in NLTK's CorpusReader.open() allows local attackers to read arbitrary files outside the designated corpus root, affecting all versions before 3.9.4. Path boundary validation is performed lexically on the string representation of a path rather than on the resolved filesystem target, so an attacker with write access to the corpus directory can plant a symlink that passes the check yet redirects reads to sensitive files anywhere the host process can access. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires that the attacker have write access to the corpus root directory or any of its subdirectories on the host filesystem, enabling symlink creation. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The provided CVSS 4.0 vector (AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H) scores 8.6, but several metrics are in tension with the vulnerability description. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | The primary remediation is to upgrade NLTK to version 3.9.4 or later, which resolves the symlink escape by performing proper symlink resolution (os.path.realpath() or equivalent) before path boundary validation inside CorpusReader.open(); the vendor advisory at https://github.com/nltk/nltk/security/advisories/GHSA-r6gq-whwq-mvg9 confirms patch availability. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all systems and applications running NLTK and verify their version numbers; prioritize systems handling sensitive data or in production environments. …
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Same weakness CWE-59 – Improper Link Resolution Before File Access
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External POC / Exploit Code
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