CVE-2026-88809 in Rancher
Summary
by MITRE • 11/02/2026
A security vulnerability exists in the SUSE Rancher Manager meta proxy endpoint (/meta/proxy). This endpoint is intended to forward requests only to destinations that appear on a configured allowlist. The allowlist decision was evaluated in a place where it could not stop a request from being forwarded, so a rejected destination was logged but the request was still handed to the proxy's transport. This affects SUSE Rancher 2.15.0 up to 2.15.3, 2.14.0 up to 2.14.7, 2.13.0 up to 2.13.11, 2.12.0 up to 2.12.15, 2.11.0 up to 2.11.19 and potentially older EOL versions.
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Analysis
by VulDB Data Team • 11/02/2026
The vulnerability identified in SUSE Rancher Manager centers on a critical logic error within the meta proxy endpoint located at /meta/proxy. This component is designed to act as an intermediary that forwards client requests to specific backend destinations, governed by a strict allowlist mechanism intended to restrict access to authorized internal services only. The core technical flaw lies in the sequence of operations performed during request processing. Specifically, the system evaluates whether the target destination exists on the configured allowlist; however, this evaluation occurs at a stage where its result is not effectively enforced as a gatekeeper for the actual network transmission. Consequently, even when the logic determines that a requested destination is unauthorized and should be rejected, the decision to block the request fails to interrupt the subsequent handoff of the request object to the underlying HTTP transport layer. This architectural oversight means that while the system may log the rejection event as an administrative record, it proceeds to forward the malicious or unintended traffic anyway, effectively bypassing the intended security control.
This flaw represents a classic implementation error where access control checks are decoupled from their enforcement mechanism, leading to a failure in authorization logic. From a technical perspective, this allows any authenticated user with access to the Rancher web interface to craft requests that target internal services or endpoints which were not explicitly whitelisted by administrators. Because the proxy forwards these requests regardless of the allowlist verdict, an attacker can potentially interact with sensitive backend components, such as Kubernetes API servers, etcd instances, or other management plane interfaces, depending on the network topology and service exposure within the cluster. The impact is significant because it undermines the principle of least privilege by allowing lateral movement across internal services that should remain isolated from direct user-facing proxy access. This could lead to unauthorized data exfiltration, manipulation of cluster configurations, or further exploitation of vulnerabilities present in those backend services.
In terms of industry standard classifications, this vulnerability aligns with CWE-284 Improper Access Control and specifically CWE-732 Incorrect Permission Assignment for Critical Resource, as the system fails to correctly apply permissions before executing a sensitive action (network forwarding). It also maps to MITRE ATT&CK technique T1090 Proxy, where adversaries use proxy connections to avoid direct detection or to pivot through trusted systems. The ability to bypass allowlists via logic errors is often categorized under CWE-862 Missing Authorization, highlighting that the system did not properly enforce access restrictions for a specific resource.
Mitigation strategies must focus on immediate remediation and long-term architectural improvements. For affected versions ranging from 2.15.0 up to 2.15.3, 2.14.0 up to 2.14.7, 2.13.0 up to 2.13.11, 2.12.0 up to 2.12.15, and 2.11.0 up to 2.11.19, as well as potentially older end-of-life versions, the primary mitigation is to apply the vendor-provided security patch that corrects the control flow logic in the proxy handler. Administrators should ensure they are running a version where the allowlist check properly terminates request processing for non-whitelisted destinations before any transport layer interaction occurs. In addition to updating software, organizations should review their network segmentation policies to limit exposure of internal management interfaces, ensuring that even if such a vulnerability is exploited in other contexts, lateral movement remains constrained. Regular auditing of proxy logs can also help detect attempts to exploit this flaw by monitoring for high volumes of rejected requests or unusual traffic patterns directed at non-standard ports or services.