JavaScript execution via prototype-polluted chart data
Published Jul 8, 2026 · Updated Jul 8, 2026
Cross-site scripting in GCHQ CyberChef before 11.2.0 allows attackers to execute JavaScript through a crafted local recipe. The Series Chart CSV parser assigns an attacker-controlled proto key to ordinary objects, and objToTable later inserts inherited keys and values into HTML without escaping. Exploitation requires a user to open attacker-supplied recipe data and run the chained operations, after which the script executes in the CyberChef browser context.
Summary
What happened
Cross-site scripting in GCHQ CyberChef before 11.2.0 allows attackers to execute JavaScript through a crafted local recipe. The Series Chart CSV parser assigns an attacker-controlled proto key to ordinary objects, and objToTable later inserts inherited keys and values into HTML without escaping. Exploitation requires a user to open attacker-supplied recipe data and run the chained operations, after which the script executes in the CyberChef browser context.
The record
- CVE
- CVE-2026-57439
- Published
- Jul 8, 2026
- Updated
- Jul 8, 2026
- Vendor
- GCHQ
- Product
- CyberChef
- Classifications
- CWE-1321, CWE-79, T1059.007, T1204.001
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 8, 2026CVE publishedPublication date reported by the CVE source.
- Jul 8, 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=< 11.2.0
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
- CyberChef Series Chart and Parse UDP 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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