CVE-2026-57439 CyberChef: Prototype pollution in Series Chart operation
Prototype pollution in CyberChef's Series Chart operation allows attackers to inject malicious JavaScript into HTML output via crafted CSV input.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-57439?
CVE-2026-57439 is a medium-severity code injection vulnerability in gchq CyberChef, published on 8 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
CyberChef is a web app for encryption, encoding, compression, and data analysis. Prior to 11.2.0, the Series Chart operation accepts __proto__ as a key while parsing user-supplied CSV, allowing prototype pollution that can be chained with operations such as Parse UDP to inject malicious JavaScript into HTML output. This issue is fixed in version 11.2.0.
Which versions are affected by CVE-2026-57439?
2 open source packages ship an affected version, including cyberchef.
| Package | Affected | Fixed in |
|---|---|---|
cyberchef npm | All versions | 11.2.0 |
cyberchef npm | All versions | 11.2.0 |
How do I fix CVE-2026-57439?
Upgrade cyberchef to 11.2.0 or later.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-57439 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-57439 exists.
Sources
Also known as GHSA-fx6f-382r-j72c.