Code execution via nested Grammar.loads payload
Published Jul 4, 2026 · Updated Jul 4, 2026
Detection bypass in picklescan before 0.0.29 allows remote attackers to conceal code execution in malicious pickle files. The scanner accepts Grammar.loads as the outer reduce callable without inspecting the nested pickle bytes passed to it, leaving a dangerous inner reduce unreported. Exploitation requires a recipient to trust the clean scan result and deserialize the file; the embedded callable then runs with that process's privileges.
Summary
What happened
Detection bypass in picklescan before 0.0.29 allows remote attackers to conceal code execution in malicious pickle files. The scanner accepts Grammar.loads as the outer reduce callable without inspecting the nested pickle bytes passed to it, leaving a dangerous inner reduce unreported. Exploitation requires a recipient to trust the clean scan result and deserialize the file; the embedded callable then runs with that process's privileges.
The record
- CVE
- CVE-2025-71359
- Published
- Jul 4, 2026
- Updated
- Jul 4, 2026
- Vendor
- Matthieu Maitre
- Product
- picklescan
- Classifications
- CWE-502, T1204.002
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 4, 2026CVE publishedPublication date reported by the CVE source.
- Jul 4, 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=0 <0.0.29
What conditions does exploitation require?
What is affected?
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.
Public exploit references
- Grammar.loads nested-pickle proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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