CVE-2026-61400: Apache CloudStack RCE Vulnerability

CVE-2026-61400 Overview

CVE-2026-61400 is a command injection vulnerability [CWE-77] in Apache CloudStack affecting the getDiagnosticsData and runDiagnostics APIs used against system VMs and Virtual Routers. An authenticated user holding the required permissions can inject arbitrary shell commands that execute on the target instance as root or, at minimum, as the diagnostics-process user. Successful exploitation results in full compromise of the affected system VM or Virtual Router. Depending on network segmentation, attackers may pivot laterally within the CloudStack-managed infrastructure and intercept guest network traffic handled by the compromised Virtual Router. The affected APIs are restricted to Admin role accounts by default.

Critical Impact
Authenticated admin-role attackers can achieve arbitrary command execution as root on CloudStack system VMs and Virtual Routers, enabling full instance compromise and potential interception of tenant guest network traffic.

Affected Products

Apache CloudStack 4.20.0.0 through 4.20.3.0
Apache CloudStack 4.21.0.0 through 4.22.1.0
CloudStack system VMs and Virtual Router instances managed by affected versions

Discovery Timeline

2026-08-21 - CVE-2026-61400 published to the National Vulnerability Database (NVD)
2026-08-27 - Last updated in NVD database

Technical Details for CVE-2026-61400

Vulnerability Analysis

The flaw resides in the CloudStack diagnostics workflow that dispatches operator-supplied parameters to shell utilities running inside system VMs and Virtual Routers. The getDiagnosticsData API retrieves diagnostic files and logs, while runDiagnostics executes network diagnostic utilities such as ping, traceroute, or arping against operator-specified targets. Input passed to these APIs is concatenated into shell command strings without adequate neutralization of special characters.

An authenticated caller with the getDiagnosticsData or runDiagnostics permission can embed shell metacharacters in API arguments to break out of the intended command context. The injected payload executes on the target system VM or Virtual Router with the privileges of the diagnostics process, which typically runs as root. Because Virtual Routers handle tenant guest network traffic including DHCP, DNS, and routing, compromise of a Virtual Router exposes traffic belonging to hosted workloads.

Root Cause

The root cause is improper neutralization of special elements used in a command [CWE-77]. Parameters supplied to getDiagnosticsData and runDiagnostics are interpolated directly into shell invocations rather than passed as separate argv elements or validated against a strict allowlist. Shell metacharacters such as ;, |, &, $(), and backticks retain their meaning when the command string reaches the shell.

Attack Vector

Exploitation requires network access to the CloudStack management API and an authenticated account holding permission to call the diagnostics APIs. By default only Admin role accounts hold these permissions, so exploitation depends on compromised or malicious admin credentials, or on non-default role configurations that grant these APIs to lower-privileged users. The attacker submits a crafted API request whose payload includes shell metacharacters, and the injected commands run inside the targeted system VM or Virtual Router. See the Apache Mailing List Thread for the vendor advisory.

Detection Methods for CVE-2026-61400

Indicators of Compromise

CloudStack management server audit log entries showing getDiagnosticsData or runDiagnostics API calls with parameters containing shell metacharacters such as ;, |, &&, $(, or backticks.
Unexpected child processes spawned by the diagnostics process on system VMs or Virtual Routers, such as sh, bash, wget, curl, nc, or python.
New or modified files under writable paths on system VMs and Virtual Routers, including /tmp, /var/tmp, and /root.
Outbound connections initiated from Virtual Router or system VM IP addresses to hosts unrelated to normal CloudStack operations.

Detection Strategies

Parse CloudStack API audit logs for runDiagnostics and getDiagnosticsData calls and alert on parameter values containing shell metacharacters or long non-ASCII sequences.
Correlate diagnostics API calls with process execution telemetry from system VMs to flag command chains that do not match the expected ping, arping, or traceroute invocations.
Baseline normal admin API usage patterns and alert on diagnostics calls issued outside change windows or from unusual source addresses.

Monitoring Recommendations

Forward CloudStack management server logs and system VM shell audit logs to a centralized analytics platform for retention and correlation.
Monitor Virtual Router instances for unexpected listening sockets, cron entries, and modifications to iptables rules.
Track authentication events for admin-role CloudStack accounts and alert on new session locations or off-hours activity.

How to Mitigate CVE-2026-61400

Immediate Actions Required

Upgrade Apache CloudStack to version 4.20.3.1, 4.22.1.1, or later as directed by the vendor advisory.
Rotate credentials for all admin-role CloudStack accounts and review recent use of getDiagnosticsData and runDiagnostics.
Audit custom role definitions to confirm that non-admin roles have not been granted permission to invoke the diagnostics APIs.
Inspect existing system VMs and Virtual Routers for signs of tampering and rebuild any instance whose integrity cannot be verified.

Patch Information

Apache has released fixed versions 4.20.3.1 and 4.22.1.1. Operators running any release in the 4.20.0.0 through 4.20.3.0 range or the 4.21.0.0 through 4.22.1.0 range must upgrade. Refer to the Apache Mailing List Thread for release notes and upgrade guidance.

Workarounds

Restrict network access to the CloudStack management API so that only trusted operator workstations can reach it.
Enforce multi-factor authentication on all admin-role accounts to reduce risk of credential-based abuse.
Remove getDiagnosticsData and runDiagnostics permissions from any custom roles that do not require them until the upgrade is applied.
After patching, redeploy system VMs and Virtual Routers so that any instances previously reachable by a vulnerable code path are replaced with clean images.

bash

# Example: verify installed CloudStack management server version
rpm -q cloudstack-management || dpkg -l | grep cloudstack-management

# Example: list roles that currently permit the affected APIs
cmk list rolepermissions | grep -Ei 'runDiagnostics|getDiagnosticsData'