Prototype pollution via unchecked nested query keys
Published Apr 23, 2021 · Updated Aug 14, 2025
Prototype pollution in Ace Metrix jquery-deparam 0.5.1 allows attackers to modify Object.prototype through a crafted query string. The deparam parser splits bracketed keys and repeatedly assigns cur[key] without rejecting proto or constructor[prototype], so traversal reaches the shared prototype. Exploitation requires an application to pass attacker-controlled parameters to deparam; inherited properties can then alter application logic.
Summary
What happened
Prototype pollution in Ace Metrix jquery-deparam 0.5.1 allows attackers to modify Object.prototype through a crafted query string. The deparam parser splits bracketed keys and repeatedly assigns cur[key] without rejecting proto or constructor[prototype], so traversal reaches the shared prototype. Exploitation requires an application to pass attacker-controlled parameters to deparam; inherited properties can then alter application logic.
The record
- CVE
- CVE-2021-20087
- Published
- Apr 23, 2021
- Updated
- Aug 14, 2025
- Vendor
- Ace Metrix
- Product
- jquery-deparam
- Classifications
- CWE-1321
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Apr 23, 2021CVE publishedPublication date reported by the CVE source.
- Aug 14, 2025Record 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=0.5.1
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
- jquery-deparam 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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