CVE-2026-21858: n8n Vulnerable to Unauthenticated File Access via Improper Webhook Request Handling

Should you act?

High exploit likelihood

EPSS ranks it in the top 5% of all CVEs for likely exploitation in the next 30 days. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 78.2%, percentile 99.6: FIRST’s model estimates a 78.2% chance of exploitation activity in the next 30 days, higher than 99.6% of all scored CVEs (very high). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes n8n (npm) >= 1.65.0, < 1.121.0, fixed in 1.121.0. Check your lockfile, including transitive dependencies.
• Editorial verdict: Act now. Ni8mare: n8n Unauthenticated Takeover, Plus a KEV RCE — If you self-host n8n and anything about it is reachable from the internet, upgrade today: one bug lets strangers in through public forms, and its companion RCE is on CISA's exploited list.

What it is

n8n is an open source workflow automation platform. Versions starting with 1.65.0 and below 1.121.0 enable an attacker to access files on the underlying server through execution of certain form-based workflows. A vulnerable workflow could grant access to an unauthenticated remote attacker, resulting in exposure of sensitive information stored on the system and may enable further compromise depending on deployment configuration and workflow usage. This issue is fixed in version 1.121.0.

From the GitHub advisory

Impact A vulnerability in n8n allows an attacker to access files on the underlying server through execution of certain form-based workflows. A vulnerable workflow could grant access to an unauthenticated remote attacker. This could result in exposure of sensitive information stored on the system and may enable further compromise depending on deployment configuration and workflow usage.

Patches The issue has been fixed in n8n version 1.121.0. Users should upgrade to this version or later to remediate the vulnerability.

Workarounds No official workarounds are available. As a temporary mitigation, users may restrict or disable publicly accessible webhook and form endpoints until upgrading.

Weakness type: CWE-20.

Product: n8n (npm) · Assigned by: GitHub_M · Published: 2026-01-07

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 78.19% probability of exploitation activity in the next 30 days; percentile 99.6.

Timeline

• 2026-01-07 — CVE record published by GitHub_M
• 2026-01-07 — GitHub-reviewed advisory GHSA-v4pr-fm98-w9pg published (critical)
• 2026-01-07 — erroneo.us brief: Ni8mare: n8n Unauthenticated Takeover, Plus a KEV RCE
• 2026-01-12 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-v4pr-fm98-w9pg github.com
2. CVE.org record CVE-2026-21858 cve.org
3. NVD entry CVE-2026-21858 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. cyera.com cyera.com

Critical npm advisories · Today’s Security Digest