External risk intelligence

Apache CloudStack SSRF in Webhook Module

CVE advisorySeverity: CRITICAL (CVSS 9.1)

CVE-2026-59085

Apache CloudStack is a cloud management platform that typically manages infrastructure via web-based interfaces and API services. Webhook modules in such platforms are designed to process external delivery requests, making them common endpoints for interaction in network-connected cloud management environments.

Server-Side Request Forgery

Apache Cloudstack

4.20.0.0 to before 4.20.3.14.21.0.0 to before 4.22.1.1

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A critical vulnerability exists in the webhook functionality of Apache CloudStack, a cloud management platform. This issue could allow unauthorized access to internal resources by exploiting how the system handles external requests. The primary concern is determining if your environment utilizes this specific function.

An issue with how CloudStack handles external requests.
Could allow unauthorized access to internal resources.
Confirm if your environment uses this feature.

Attack Path

How an attacker could exploit the issue

An attacker can exploit this vulnerability by sending specially crafted webhook delivery requests to the Apache CloudStack webhook module. This could allow them to induce the server to make unintended network requests, potentially leading to unauthorized access to sensitive information or internal resources.

The attacker needs network access.
Triggered by webhook delivery requests.
Risk of unintended server network requests.

Live Threat

Current exploitation, exposure, and threat context

A server-side request forgery vulnerability in Apache CloudStack's webhook module could allow an attacker to make the server send requests to arbitrary internal or external resources. This could occur when webhook delivery requests are not properly validated, potentially exposing internal network details or enabling unauthorized access to connected services.

Internal network resources may be exposed.
Malicious requests could be sent by the server.
Unauthorized access to connected services.

Operational Fix

Recommended remediation, mitigation, and detection steps

This Server-Side Request Forgery vulnerability in Apache CloudStack's webhook module requires immediate attention from teams managing cloud infrastructure and application delivery. The first step is to identify all instances of the affected Apache CloudStack versions, confirm their network exposure and business criticality, and then assign ownership for remediation.

Cloud infrastructure and platform teams own.
Verify webhook module exposure and criticality.
Plan upgrade or apply vendor-recommended fix.

Supplementary metadata

CVSS vector

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Frequently asked questions

What is Apache CloudStack and its webhook module?

Apache CloudStack is a widely used open-source cloud computing platform that manages large-scale virtualized infrastructure. It provides self-service portals and APIs to manage virtual machines, storage, and networking. The webhook module acts as a communication bridge, allowing the platform to send automated notifications or data to external services when specific cloud events occur.

What does CVE-2026-59085 mean for security?

This CVE represents a Server-Side Request Forgery (SSRF) vulnerability, categorized as CWE-918. It means the software can be tricked into acting as a proxy, forcing the server to send network requests to destinations it was not intended to reach. Because the server itself initiates these requests, it may bypass typical firewalls or security controls protecting internal systems.

How is the Apache CloudStack vulnerability triggered?

The vulnerability is triggered when an attacker sends a specially crafted webhook delivery request to the platform. By manipulating these requests, an attacker can influence the server's outbound traffic. Notably, this flaw is not triggered by standard administrative operations or normal system background tasks; it specifically requires the processing of malicious webhook requests.

Is my environment at risk based on Halo Surface Signal?

Halo Surface Signal indicates that Apache CloudStack instances are typically managed through web interfaces and APIs, making them frequent points of network interaction. Because the webhook module is designed to communicate with external endpoints, any CloudStack deployment with reachable API or webhook services faces a higher risk of being used as an unauthorized gateway to internal resources.

What should I do if I run affected Apache CloudStack versions?

You should begin by identifying all instances of the platform running versions 4.20.0.0 through 4.20.3.0 or 4.21.0.0 through 4.22.1.0 in your environment. Once identified, evaluate the necessity of the webhook feature and prioritize upgrading to the patched versions, specifically 4.20.3.1, 4.22.1.1, or later, to resolve the underlying request validation flaw.

References

lists.apache.org/thread/g6cwddtjrwbh1d56wjz4cfp3fzfm4kbc

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.