Object prototype modification via unguarded recursive merge
Published Aug 25, 2026 · Updated Aug 25, 2026
Prototype pollution in Cleverbrush @cleverbrush/deep 4.0 through 4.4.0 allows attackers to modify Object.prototype through untrusted input. The deepExtend helper recursively follows an inherited proto accessor when merging a source object's enumerable keys, then writes attacker-named properties onto Object.prototype. Reachability requires a consuming application to pass attacker-controlled object data to deepExtend; downstream effects depend on property lookups and available gadgets.
Summary
What happened
Prototype pollution in Cleverbrush @cleverbrush/deep 4.0 through 4.4.0 allows attackers to modify Object.prototype through untrusted input. The deepExtend helper recursively follows an inherited proto accessor when merging a source object's enumerable keys, then writes attacker-named properties onto Object.prototype. Reachability requires a consuming application to pass attacker-controlled object data to deepExtend; downstream effects depend on property lookups and available gadgets.
The record
- CVE
- CVE-2026-78654
- Published
- Aug 25, 2026
- Updated
- Aug 25, 2026
- Vendor
- Cleverbrush
- Product
- Cleverbrush Framework
- Classifications
- CWE-1321, CWE-94
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 25, 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=4.0
- Affected versionversion=4.1
- Affected versionversion=4.2
- Affected versionversion=4.3
- Affected versionversion=4.4.0
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
- Benign deepExtend __proto__ proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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