CyberChef: Prototype pollution in Series Chart operationGHSA-fx6f-382r-j72c
MEDIUMFix: gchq/CyberChef#2569GHSA-fx6f-382r-j72c is a medium-severity (CVSS 5) Cross-site Scripting (XSS) vulnerability in cyberchef. A fix is available for cyberchef — see the affected versions and patch details below.
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for GHSA-fx6f-382r-j72c.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-fx6f-382r-j72c by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
cyberchefnpmDescription
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)>,1
Impact
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 Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | cyberchef | all versions | 11.2.0npm install cyberchef@11.2.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for cyberchef, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update cyberchef to 11.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fx6f-382r-j72c is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is GHSA-fx6f-382r-j72c in your dependencies?
Find it across npm, including transitive dependencies.