Prototype pollution via unchecked __proto__ deep merge
Published Aug 13, 2026 · Updated Aug 13, 2026
Prototype pollution in Quasar before 2.22.0 allows attackers to alter shared object defaults through attacker-controlled deep merges. The public extend() utility in ui/src/utils/extend/extend.js recursively follows an own proto key and assigns its nested properties to Object.prototype. Reachability requires an application to pass user-controlled objects to extend(true, ...); polluted properties can then cause logic bypass, unsafe default injection, or a service crash.
Summary
What happened
Prototype pollution in Quasar before 2.22.0 allows attackers to alter shared object defaults through attacker-controlled deep merges. The public extend() utility in ui/src/utils/extend/extend.js recursively follows an own proto key and assigns its nested properties to Object.prototype. Reachability requires an application to pass user-controlled objects to extend(true, ...); polluted properties can then cause logic bypass, unsafe default injection, or a service crash.
The record
- CVE
- CVE-2026-73647
- Published
- Aug 13, 2026
- Updated
- Aug 13, 2026
- Vendor
- Quasar Framework
- Product
- Quasar
- Classifications
- CWE-1321
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 13, 2026CVE publishedPublication date reported by the CVE source.
- Aug 13, 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?
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- Affected versionversion=< 2.22.0
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
- Quasar extend() prototype-pollution proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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