CVE-2026-61398 in CloudStack
Summary
by MITRE • 08/21/2026
Improper Encoding or Escaping of Output vulnerability in Apache CloudStack's UI while using Instance Reset Password functionality.
This issue affects Apache CloudStack: from 4.15.1.0 through 4.20.3.0 and from 4.21.0.0 through 4.22.1.0.
Users are recommended to upgrade to version 4.20.3.1 or 4.22.1.1 or later, which fixes the issue.
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Analysis
by VulDB Data Team • 08/22/2026
The vulnerability identified in Apache CloudStack represents a critical failure in input validation and output encoding mechanisms within the platform's web-based user interface. Specifically, this flaw resides in the implementation of the Instance Reset Password functionality, a feature designed to allow administrators or users to reset credentials for virtual machine instances managed by the cloud infrastructure. The core technical deficiency is an improper encoding or escaping of output data when rendering responses related to password resets. In secure software development, any dynamic content generated from user-supplied input or internal state must be properly encoded before being inserted into HTML contexts to prevent malicious scripts from executing within the victim's browser session. Apache CloudStack versions ranging from 4.15.1.0 through 4.20.3.0 and from 4.21.0.0 through 4.22.1.0 are susceptible because they fail to apply adequate sanitization or encoding protocols when processing the output of this specific administrative action, leaving a window for exploitation by attackers who can interact with the UI.
From an operational perspective, this vulnerability enables Cross-Site Scripting attacks against users accessing the Apache CloudStack management console. An attacker could craft a malicious payload that exploits the lack of proper escaping in the Instance Reset Password response. When a privileged user or administrator views the affected page after triggering the reset operation, the injected script would execute within their browser context under the authority of the cloud platform session. This capability allows for significant security breaches including session hijacking, where an attacker steals authentication cookies to impersonate legitimate users; credential theft via keylogging scripts embedded in the payload; and potentially arbitrary code execution if combined with other vulnerabilities or specific browser exploits. The impact is particularly severe because it targets administrative interfaces often used by highly privileged accounts responsible for managing critical cloud resources, thereby escalating the risk from a simple client-side issue to a potential compromise of the entire virtualization infrastructure.
This flaw aligns directly with Common Weakness Enumeration category CWE-79, which classifies Improper Neutralization of Input During Web Page Generation known as Cross-site Scripting (XSS). The failure occurs specifically in the output encoding phase rather than input validation, highlighting a gap in the defense-in-depth strategy employed by the application. Furthermore, from an adversary tactics perspective, this vulnerability facilitates techniques described in MITRE ATT&CK framework under T1059 Command and Control or potentially T1204 User Execution if social engineering is involved to lure administrators into triggering specific states that expose the vulnerable output. The exploitation does not require complex network-level attacks but relies on web-based interaction, making it accessible to a broader range of threat actors who may have gained limited access to the management UI through phishing or other initial compromise vectors.
To mitigate this risk and restore secure operations within the Apache CloudStack environment, immediate action is required by upgrading the affected software components. The vendor has released patched versions that address these encoding deficiencies in subsequent releases. Organizations running any version from 4.15.1.0 up to 4.20.3.0 should upgrade directly to version 4.20.3.1 or later. Similarly, environments operating on the newer branch starting with 4.21.0.0 must be upgraded to at least version 4.22.1.1 or a more recent stable release. These updates incorporate rigorous input validation and output encoding practices that neutralize the potential for script injection within the Instance Reset Password workflow. Until upgrades are performed, administrators should consider implementing strict Content Security Policy headers if supported by their deployment architecture to limit script execution sources, although this is only a compensating control and does not replace the need for patching the underlying application code vulnerability.