CVE-2026-78545 in Access Gateway
Summary
by MITRE • 09/08/2026
The Okta Access Gateway does not sanitize the application label field before including it in the generated nginx configuration file. The unsanitized value is interpolated into an nginx server block directive, resulting in execution of injected directives.
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Analysis
by VulDB Data Team • 09/08/2026
This vulnerability represents a critical injection flaw within the Okta Access Gateway software, specifically affecting how the system handles user-defined application labels during the generation of backend Nginx configuration files. The core technical deficiency lies in the absence of proper input validation and sanitization routines for the application label field before it is interpolated into server block directives. When an administrator or automated process assigns a maliciously crafted string to this field, the gateway fails to escape special characters that hold syntactic significance within the Nginx configuration language. Consequently, these unsanitized inputs are treated as valid configuration commands rather than literal data strings, allowing attackers to inject arbitrary Nginx directives directly into the active server block context.
The operational impact of this flaw is severe because it effectively grants an attacker with access to the application label configuration interface the ability to manipulate the web server's behavior at a low level. By injecting specific directives, such as proxy_pass or rewrite rules, an adversary can redirect traffic to malicious endpoints, intercept sensitive authentication tokens and session cookies in transit, or bypass existing security controls like rate limiting and IP whitelisting that are defined elsewhere in the configuration. This capability transforms what appears to be a simple metadata field into a potent vector for man-in-the-middle attacks and data exfiltration, compromising the integrity of all applications proxied through this specific gateway instance.
From a classification perspective, this vulnerability aligns with CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component, as it involves the failure to neutralize special elements that could alter the interpretation of output intended for another system component, specifically Nginx. Furthermore, the exploitation technique maps closely to ATT&CK T1505.003 Server Message Block (SMB) Services or more accurately in this context, web server configuration manipulation which falls under techniques related to persistence and defense evasion through infrastructure compromise. The attacker leverages trusted administrative interfaces to modify system configurations, thereby establishing a foothold that persists across service restarts unless the malicious directives are manually removed from the generated files.
Mitigation strategies must prioritize immediate patching of the Okta Access Gateway software to versions where this input sanitization logic has been corrected. In environments where patching is not immediately feasible, administrators should implement strict allow-listing for application label inputs at the API or UI level to prevent the submission of strings containing characters such as curly braces, semicolons, and backslashes that are critical to Nginx syntax. Additionally, deploying a Web Application Firewall with rules capable of detecting configuration injection patterns in administrative traffic can provide an additional layer of defense by blocking requests that attempt to inject structural elements into backend service configurations. Regular auditing of generated configuration files for unexpected directives is also recommended to detect any successful exploitation attempts early.