CyberChef: Prototype pollution in Series Chart operation
On 5 June 2026 CyberChef received a security vulnerability report from @hyuunnn detailing a vulnerability in the Series Chart operation, where malicious input could result in prototype pollution of the data structures outputted from the operation. Other operations following Series Chart could have their behaviour manipulated by the attacker-controlled prototype, for example, injecting malicious content into their HTML output.
In this case, a demonstration was provided that chained the Series Chart operation with the Parse UDP operation to cause attacker controlled JavaScript to be executed.
Details
When the Series Chart operation parses user-supplied CSV, it accepts __proto__ as a key and uses it to pollute the object.
The objToTbale function in src/core/lib/Protocol.mjs, used in a number of IP parsing operations, renders data items within <td> tags without escaping.
These bugs can be chained to produce an XSS vulnerability.
Encoded input data is:
__proto__,<img src=x onerror=alert(document.domain)>,1Impact
Objects with attacker controlled prototypes could be processed by CyberChef operations. This enabled control of the output of some operations, and in particular, the ability to insert malicious JavaScript into the output of the Parse UDP operation.
Patches
This has been patched in release v11.2.0.
Workarounds
No workarounds are available. Users must upgrade to CyberChef v11.2.0.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | cyberchef | < 11.2.0 | 11.2.0 |
References
- https://github.com/gchq/CyberChef/security/advisories/GHSA-fx6f-382r-j72c
- https://nvd.nist.gov/vuln/detail/CVE-2026-57439
- https://github.com/gchq/CyberChef/issues/2568
- https://github.com/gchq/CyberChef/pull/2569
- https://github.com/gchq/CyberChef/commit/85db3be5d0096859b810f0e8d3e151d5dc9b948f
- https://github.com/gchq/CyberChef
- https://github.com/gchq/CyberChef/releases/tag/v11.2.0
- CVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N- Weakness (CWE)
CWE-1321, CWE-79- Platform
- npm
- Package
cyberchef- Disclosed
- 24.09.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-fx6f-382r-j72c - CC BY 4.0
Vulnerability history: cyberchef
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 3
- First → latest
- 08.2019 09.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 1
- Medium 2
Disclosures per year
- 2019: 1
- 2020: 0
- 2021: 0
- 2022: 0
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 2
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