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Ni8mare and N8scape flaws among multiple critical vulnerabilities affecting n8n
rapid7.comadvisory

Ni8mare and N8scape flaws among multiple critical vulnerabilities affecting n8n

Rapid7's ETR write-up on "Ni8mare," an exploit chain against n8n automation software anchored by CVE-2026-21858 (CVSS 10.0), an unauthenticated file read flaw triggered by improper content-type validation on custom webhook file-upload forms that lets an attacker overwrite internal JSON to read arbitrary files and forge admin session tokens. That access can be chained with four authenticated CVEs — CVE-2025-68613 (expression language injection RCE), CVE-2025-68668 (Pyodide Python node command execution), CVE-2025-68697 (legacy Code node file read/write), and CVE-2026-21877 (arbitrary file write RCE, CVSS 9.9) — for full remote code execution. Cyera and researcher Valentin Lobstein published separate technical analyses and PoCs on the same day; Rapid7 lists affected version ranges for each CVE and recommends upgrading self-hosted n8n to 1.121.0+.

TL;DR Chained n8n exploit "Ni8mare" combines an unauthenticated file-read bug (CVE-2026-21858, CVSS 10.0) with four authenticated CVEs to reach full RCE.
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What it is

Five CVEs affecting n8n automation software, anchored by CVE-2026-21858 ("Ni8mare," CVSS 10.0), an unauthenticated arbitrary file read. The patch shipped November 18, 2025; the advisory was published January 7, 2026. The summary names all five CVEs and their mechanisms — what it omits is the per-CVE affected version ranges and one operational nuance about which authenticated bug is realistic to chain.

Preconditions / Affected

Per-CVE version boundaries (vendor-stated), which the summary does not carry:

  • CVE-2026-21858 (unauth file read, CVSS 10.0): ≥1.65.0 and <1.121.0. Requires a custom web form that implements file uploads without content-type validation.
  • CVE-2025-68613 (expression injection RCE): ≥0.211.0 and <1.20.4.
  • CVE-2025-68668 (Pyodide Python node command exec): ≥1.0.0 and <2.0.0.
  • CVE-2025-68697 (legacy Code node file read/write): ≥1.2.1 and <2.0.0.
  • CVE-2026-21877 (arbitrary file write RCE, CVSS 9.9): ≥0.123.0 and <1.121.3 — affects both self-hosted and cloud n8n.

Note the ranges do not all overlap: CVE-2025-68613's ceiling (<1.20.4) sits below CVE-2026-21858's floor (≥1.65.0), so the specific chain each bug enables depends on the target's exact version.

What to do

Upgrade self-hosted n8n to ≥1.121.0 to close the unauthenticated initial-access vector (CVE-2026-21858). Rapid7 Exposure Command, InsightVM, and Nexpose customers have vulnerability checks for all five CVEs in the January 9, 2026 content release.

Caveats

  • CVE-2025-68697 is the least practical link in the chain. It only applies when the Code node runs in legacy (non-task-runner) JavaScript mode, and since n8n ≥1.2.1 blocks read/write to the .n8n directory by default, Rapid7 assesses that exploiting it as a chained secondary bug would require a bespoke per-target strategy — making it unlikely versus the other authenticated CVEs.
  • Only two exploits were public as of writing: Cyera's writeup demonstrates CVE-2026-21858 alone; Valentin Lobstein's PoC additionally chains CVE-2025-68613 for RCE. The other three authenticated CVEs are described as chainable but no PoC is cited.

Organisations named here

  • Cyera
  • Ni8mare
  • Valentin Lobstein

CVEs named here

  • CVE-2026-21858
  • CVE-2025-68613
  • CVE-2025-68668
  • CVE-2025-68697
  • CVE-2026-21877

Technologies named here

  • n8n
  • Exposure Command
  • InsightVM
  • Nexpose

Techniques named here

  • Expression language injection
  • File read/write via legacy Code node execution mode
  • RCE via arbitrary file write
  • Vulnerability chaining

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