Remote code execution via dotted-name allowlist bypass
Published Aug 22, 2026 · Updated Aug 25, 2026
Deserialization in NLTK 3.10.0 through 3.10.2 allows remote attackers to execute arbitrary commands through a crafted parser model. AllowlistUnpickler.find_class checks the pickle module against a prefix allowlist but accepts dotted global names, letting attribute traversal reach sklearn.os.system. Execution requires an application to pass an attacker-controlled transition-parser model to TransitionParser.parse.
Summary
What happened
Deserialization in NLTK 3.10.0 through 3.10.2 allows remote attackers to execute arbitrary commands through a crafted parser model. AllowlistUnpickler.find_class checks the pickle module against a prefix allowlist but accepts dotted global names, letting attribute traversal reach sklearn.os.system. Execution requires an application to pass an attacker-controlled transition-parser model to TransitionParser.parse.
The record
- CVE
- CVE-2026-71513
- Published
- Aug 22, 2026
- Updated
- Aug 25, 2026
- Vendor
- NLTK Project
- Product
- NLTK
- Classifications
- CWE-502, T1203
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 22, 2026CVE publishedPublication date reported by the CVE source.
- Aug 25, 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=3.10.0 <3.10.3
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
- Pruva CVE-2026-71513 reproductionproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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