CVE-2026-88804 in Rancher
Summary
by MITRE • 09/28/2026
An unauthenticated update of public UI settings could be used by remote attackers to execute a stored cross-site scripting attack in the Rancher UI, in SUSE Rancher 2.15 before 2.15.2, 2.14 before 2.14.6, 2.13 before 2.13.10, 2.12 before 2.12.14 and 2.11 before 2.11.18.
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Analysis
by VulDB Data Team • 09/28/2026
The vulnerability identified in SUSE Rancher versions prior to 2.15.2, 2.14.6, 2.13.10, 2.12.14, and 2.11.18 represents a critical security flaw within the web-based management interface of the container orchestration platform. This issue stems from an insufficient validation mechanism applied to public user interface settings that are updated via unauthenticated API endpoints or requests. Because these specific configuration parameters do not require authentication for modification, any remote actor with network access to the Rancher server can manipulate them without providing valid credentials. The core technical flaw lies in the failure to sanitize input data before it is stored and subsequently rendered by the browser-based frontend of the application. This lack of proper output encoding allows malicious scripts to be embedded within these settings fields, which are then persisted on the server side for future retrieval and display.
This architectural weakness directly facilitates a Stored Cross-Site Scripting attack vector. Unlike reflected XSS where the payload is delivered via a crafted link that must be clicked by a victim, stored XSS persists in the application's database or configuration store. When an administrator or any other authenticated user logs into the Rancher UI to manage clusters, nodes, or workloads, the browser retrieves these tainted settings and renders them as part of the page content. The malicious JavaScript code executes automatically within the context of the victim’s session, leveraging the trust that browsers place in scripts originating from the same domain as the application interface. This execution environment grants the attacker significant capabilities to interact with the DOM elements of the Rancher UI on behalf of the logged-in user.
The operational impact of this vulnerability is severe due to the high-privilege nature of typical Rancher administrators. An attacker can exploit this flaw to steal session cookies, authentication tokens, or other sensitive credentials stored in local storage or cookies associated with the Rancher domain. With these stolen artifacts, the adversary can hijack administrative sessions and gain full control over the Kubernetes clusters managed by Rancher. This level of access allows for the deployment of malicious workloads, exfiltration of secrets from namespace service accounts, modification of cluster configurations to disable security controls such as network policies or admission controllers, and potentially pivoting into other systems within the internal network that are accessible from the compromised container infrastructure. The ability to execute arbitrary code in the context of privileged users effectively bypasses many traditional perimeter defenses since the attack originates from a trusted domain.
From a classification perspective, this vulnerability aligns with CWE-79, which describes Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting. Specifically, it falls under the sub-category of Stored XSS where malicious content is saved on target servers and later served to users. In terms of offensive security frameworks such as MITRE ATT&CK, this vulnerability supports techniques related to Collection via Browser Hijacking (T1556) for credential theft and potentially Command and Control if used to establish persistent access channels through the browser environment. The lack of authentication required for the initial exploitation step also highlights a failure in Access Control principles, though the primary risk is driven by the injection flaw itself rather than just privilege escalation.
Mitigation strategies must prioritize immediate patching as outlined in the vendor advisories. Administrators should upgrade SUSE Rancher to version 2.15.2 or later for the 2.15 branch, 2.14.6 for the 2.14 branch, 2.13.10 for the 2.13 branch, 2.12.14 for the 2.12 branch, and 2.11.18 for the 2.11 branch to receive the necessary input validation fixes. In environments where immediate patching is not feasible due to operational constraints, temporary mitigations should focus on restricting network access to the Rancher UI management interface using firewalls or reverse proxy configurations that limit exposure only to trusted IP ranges. Additionally, implementing strict Content Security Policy headers can help mitigate the impact of any successful XSS attempts by preventing the execution of unauthorized scripts, although this is a compensating control and not a substitute for fixing the underlying input validation deficiency. Regular security audits of API endpoints should also be conducted to ensure no other unauthenticated write operations exist that could lead to similar injection vulnerabilities in future updates or related components.