CVE-2026-15743 in Static-Simple
Summary
by MITRE • 08/20/2026
Catalyst::Plugin::Static::Simple versions through 0.38 for Perl mark responses as publicly cacheable.
The _serve_static method always sets the Cache-Control header to "public", with no means of overriding it. This advises proxies that the content may be stored in a shared cache, and may be reused in responses to requests from other users. (This includes requests with an Authorization header.)
Configuring the expires time to "0" to disable caching, as documented, is ignored.
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Analysis
by VulDB Data Team • 08/20/2026
The vulnerability identified in Catalyst::Plugin::Static::Simple versions through 0.38 represents a critical misconfiguration of HTTP cache control headers that exposes sensitive web application content to unauthorized access via shared proxy caches. This Perl module, commonly used for serving static assets within the Catalyst web framework, contains a hardcoded logic flaw in its _serve_static method where it unconditionally sets the Cache-Control header value to public. By marking responses as publicly cacheable, the plugin instructs intermediate caching proxies and CDNs that the content is safe to store and serve to any subsequent requester, regardless of the original request's context or authentication status. This behavior fundamentally contradicts security best practices for serving dynamic or potentially sensitive static resources, such as configuration files, user-specific data exports, or internal documentation, which should never be cached by third-party intermediaries without explicit authorization checks.
The operational impact of this flaw is severe because it bypasses standard HTTP caching mechanisms designed to protect private content. When a proxy receives a response marked with Cache-Control: public, it stores the resource in its shared memory pool. Subsequently, if another user requests the same URL, even one that includes an Authorization header indicating they are authenticated and expecting personalized or restricted data, the proxy may serve the cached version from the previous request instead of forwarding the new request to the origin server. This results in a classic Broken Access Control scenario where users can inadvertently retrieve information belonging to other users or system administrators who previously accessed those resources. The flaw is exacerbated by the fact that attempts to disable caching via configuration, such as setting the expires time to zero, are ignored due to the hardcoded nature of the header injection logic within the plugin's source code.
From a technical classification perspective, this vulnerability aligns with CWE-524, which describes Cache Control Headers That Allow Sensitive Information Disclosure, and falls under the broader category of CWE-16, Configuration Errors. In terms of adversary tactics, this flaw facilitates data exfiltration through cache poisoning or side-channel attacks where an attacker can induce a privileged user to request specific resources, thereby caching them for later retrieval by the attacker. This maps directly to MITRE ATT&CK technique T1530, Data from Information Repositories, and potentially T1602, Screen Capture, if sensitive visual data is cached. The persistence of this issue in version 0.38 highlights a lack of rigorous security review for default configurations in widely used Perl modules, where convenience often overrides security principles regarding cache scope.
Mitigation strategies must address both the immediate code-level defect and broader architectural caching policies. For users currently running affected versions, the most effective remediation is to upgrade to a patched version of Catalyst::Plugin::Static::Simple that allows for dynamic control over Cache-Control headers or removes the public directive by default. If upgrading is not immediately feasible, administrators should implement reverse proxy configurations using tools like Nginx or Apache to override the upstream response headers. Specifically, configuring the proxy to strip or modify the Cache-Control header from responses served by this plugin can prevent shared caches from storing sensitive data. Additionally, developers should audit their application for any static resources that contain user-specific information and ensure they are either not served through vulnerable plugins or are protected with additional authentication checks before being marked as cacheable. Long-term security hygiene requires enforcing strict Cache-Control policies such as no-store or private for all responses containing potential PII or sensitive business logic, ensuring that caching is explicitly enabled only for truly public, non-sensitive assets like images and stylesheets where performance gains outweigh privacy risks.