CVE-2026-39749 in App Plugin
Summary
by MITRE • 10/06/2026
Subscriber Broken Access Control in App for Cloudflare® <= 1.10.1 versions.
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Analysis
by VulDB Data Team • 10/06/2026
The vulnerability identified as Subscriber Broken Access Control within the Cloudflare application, specifically affecting versions up to and including 1.10.1, represents a critical failure in enforcing proper authorization policies on the server side. This flaw allows authenticated users who possess lower privilege levels or standard subscriber roles to manipulate API requests that are intended exclusively for administrators or higher-tier account holders. The core technical issue stems from insufficient validation of user permissions during the processing of HTTP requests related to subscription management and billing configurations. When a request is received, the application fails to adequately verify whether the authenticated identity associated with the session token has the requisite authority to perform the specific action being requested. This oversight enables an attacker who has compromised or obtained valid credentials for a standard subscriber account to escalate their privileges effectively by sending crafted requests that modify critical account settings, such as changing billing information, altering subscription tiers, or accessing sensitive organizational data reserved for enterprise administrators.
From a technical perspective, this vulnerability aligns with the Common Weakness Enumeration category CWE-269, which classifies Improper Privilege Control. The root cause lies in the application logic where access control checks are either missing, bypassed, or incorrectly implemented within the backend services handling subscriber data. In many modern web applications, especially those operating on multi-tenant cloud architectures like Cloudflare, maintaining strict isolation between different user roles is paramount for security and operational integrity. Here, the lack of robust server-side authorization middleware means that client-supplied parameters indicating a desired action or target resource are accepted without sufficient scrutiny against the current user's permission set. This allows an attacker to exploit the trust placed in session identifiers by simply altering request payloads to invoke administrative endpoints. The vulnerability is particularly dangerous because it does not require any external exploitation techniques such as buffer overflows or injection attacks; instead, it relies on the fundamental misconfiguration of access control rules within the application's business logic layer.
The operational impact of this broken access control mechanism is severe and multifaceted. For individual subscribers, the immediate risk involves unauthorized changes to their own account settings which could lead to service disruption if billing details are altered incorrectly or subscription tiers are downgraded maliciously by an insider threat scenario. However, the more significant concern arises when considering multi-tenant environments where a subscriber might attempt to access data belonging to other tenants or escalate privileges to gain administrative control over shared resources. If exploited successfully, this vulnerability could lead to unauthorized modification of DNS records, SSL/TLS certificate configurations, or firewall rules for domains managed by higher-level accounts if the application architecture allows cross-account manipulation through flawed API design. Furthermore, it compromises the integrity of billing systems, potentially allowing attackers to manipulate invoice generation or payment methods, leading to financial fraud and revenue loss for both the service provider and its customers. The breach also undermines trust in the platform's security posture, as it demonstrates a failure to enforce least privilege principles essential for secure software development.
To mitigate this vulnerability, immediate patching of the Cloudflare application to version 1.10.2 or later is required, as these updates include corrected authorization logic that properly validates user roles before processing sensitive requests. In addition to applying vendor patches, organizations utilizing affected versions should implement strict input validation and enforce role-based access control checks at multiple layers within their infrastructure. This includes deploying Web Application Firewalls configured with rulesets designed to detect anomalous API usage patterns indicative of privilege escalation attempts. Security teams should also conduct thorough code reviews focusing on authentication middleware and authorization handlers to ensure that every endpoint explicitly verifies the caller's permissions against a centralized policy store rather than relying solely on client-side indicators or implicit trust models. Regular penetration testing focused on broken access control scenarios, aligned with MITRE ATT&CK techniques such as T1078 Valid Accounts and T1548 Abuse Elevation Control Mechanism, will help identify similar weaknesses in other applications within the enterprise environment before they can be exploited by malicious actors seeking to compromise critical infrastructure.