Arbitrary file overwrite via XML path traversal
Published Mar 20, 2026 · Updated Mar 20, 2026
Path traversal in the NLTK downloader 3.9.3 and earlier allows remote attackers to overwrite arbitrary files through a malicious XML index. Package initialization joins unvalidated subdir and id attributes into a filename, and _download_package joins that value to download_dir before opening it for binary writing. Exploitation requires a user or application to select an attacker-controlled index and request its crafted package; writes carry the invoking process's filesystem permissions.
Summary
What happened
Path traversal in the NLTK downloader 3.9.3 and earlier allows remote attackers to overwrite arbitrary files through a malicious XML index. Package initialization joins unvalidated subdir and id attributes into a filename, and _download_package joins that value to download_dir before opening it for binary writing. Exploitation requires a user or application to select an attacker-controlled index and request its crafted package; writes carry the invoking process's filesystem permissions.
The record
- CVE
- CVE-2026-33236
- Published
- Mar 20, 2026
- Updated
- Mar 20, 2026
- Vendor
- NLTK Project
- Product
- NLTK
- Classifications
- CWE-22, T1204.002
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 20, 2026CVE publishedPublication date reported by the CVE source.
- Mar 20, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=<= 3.9.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- GHSA-469j-vmhf-r6v7 proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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