Object prototype modification via unsanitized recursive merge
Published Apr 20, 2026 · Updated Apr 20, 2026
Prototype pollution in brikcss @brikcss/merge 1.0 through 1.3.0 allows remote attackers to modify inherited object properties. The merge function recursively copies attacker-controlled source-object keys without filtering proto, constructor.prototype, or prototype, so assignments reach Object.prototype. Exploitation requires a consuming application to pass attacker-controlled objects into the library; polluted properties then affect unrelated objects in that process.
Summary
What happened
Prototype pollution in brikcss @brikcss/merge 1.0 through 1.3.0 allows remote attackers to modify inherited object properties. The merge function recursively copies attacker-controlled source-object keys without filtering proto, constructor.prototype, or prototype, so assignments reach Object.prototype. Exploitation requires a consuming application to pass attacker-controlled objects into the library; polluted properties then affect unrelated objects in that process.
The record
- CVE
- CVE-2026-6594
- Published
- Apr 20, 2026
- Updated
- Apr 20, 2026
- Vendor
- brikcss
- Product
- @brikcss/merge
- Classifications
- CWE-94, CWE-1321
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 20, 2026CVE publishedPublication date reported by the CVE source.
- Apr 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=1.0
- Affected versionversion=1.1
- Affected versionversion=1.2
- Affected versionversion=1.3.0
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.
Weakness, pattern, technique
Public exploit references
- Prototype Pollution in brikcss/merge 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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