Security readout for executives and security teams
Plain-English summary
n8n versions 1.65.0 through before 1.121.0 can expose files from the server to an unauthenticated remote attacker when certain form-based workflows are present. This can reveal sensitive data and may support deeper compromise depending on deployment and workflow configuration. Upgrade is available in 1.121.0.
Executive priority
Treat as urgent for any internet-exposed n8n deployment. The issue is unauthenticated, remotely reachable, and rated CVSS 10.0. Prioritize upgrade and exposure reduction, then review logs and workflows for signs of sensitive data exposure.
Technical view
CVE-2026-21858 is improper input/request handling in n8n webhook processing for form-based workflows. It is network-reachable, low complexity, requires no authentication or user interaction, and has CVSS 10.0. Affected versions are >=1.65.0 and <1.121.0. The stated fixed version is 1.121.0.
Likely exposure
Internet-facing n8n instances are the main concern, especially where public form/webhook workflows are enabled. Internal instances may still be exposed to unauthenticated users on reachable networks. Impact depends on host file contents, secrets available to n8n, and workflow configuration.
Exploitation context
The bundle does not show CISA KEV listing or confirmed active exploitation. Public references include the GitHub advisory and Cyera research. The CVE describes unauthenticated file access; Cyera’s referenced title frames the issue as unauthenticated remote code execution, so teams should review both sources.
Researcher notes
Evidence supports affected range, CVSS vector, unauthenticated server file access, and fix version. The provided description does not include exploit details, indicators, or proof of active exploitation. Avoid assuming RCE in every deployment; assess impact based on workflow design and n8n host permissions.
Mitigation direction
- Upgrade n8n to version 1.121.0 or later.
- Inventory all n8n instances, including self-hosted and containerized deployments.
- Restrict network access to n8n until upgraded where feasible.
- Review public form-based workflows and disable unnecessary unauthenticated webhooks.
- Check vendor guidance for any additional configuration-specific mitigations.
Validation and detection
- Confirm running n8n versions are not >=1.65.0 and <1.121.0.
- Identify externally reachable n8n endpoints and form-based workflows.
- Review logs for unusual unauthenticated webhook or form submissions.
- Check for unexpected file access indicators around webhook activity.
- Verify upgrade completion and restart status through normal asset management records.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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Open ATT&CK lookupCVE-2026-21858 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 10 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N3.95.8Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
10CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/n8n-io/n8n/security/advisories/GHSA-v4pr-fm98-w9pgCVE reference · x_refsource_CONFIRM
- https://www.cyera.com/research-labs/ni8mare-unauthenticated-remote-code-execution-in-n8n-cve-2026-21858CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.