CVE-2023-42457 in plone.rest
Summary
by MITRE • 09/21/2023
plone.rest allows users to use HTTP verbs such as GET, POST, PUT, DELETE, etc. in Plone. Starting in the 2.x branch and prior to versions 2.0.1 and 3.0.1, when the `++api++` traverser is accidentally used multiple times in a url, handling it takes increasingly longer, making the server less responsive. Patches are available in `plone.rest` 2.0.1 and 3.0.1. Series 1.x is not affected. As a workaround, one may redirect `/++api++/++api++` to `/++api++` in one's frontend web server (nginx, Apache).
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Analysis
by VulDB Data Team • 09/21/2023
The vulnerability described in CVE-2023-42457 affects the plone.rest component within the Plone content management system, specifically impacting versions from the 2.x branch prior to 2.0.1 and 3.0.1. This issue stems from improper handling of the ++api++ traverser when it appears multiple times within a single URL path, creating a performance degradation that manifests as increasing response times for server operations. The plone.rest framework enables RESTful API access through standard HTTP methods including GET, POST, PUT, and DELETE, making it a critical component for API interactions within Plone applications. When the ++api++ traverser is invoked repeatedly in a URL such as /++api++/++api++, the system processes these nested requests inefficiently, leading to resource consumption that grows exponentially with each additional traverser instance.
The technical flaw represents a classic denial of service vulnerability that operates through resource exhaustion rather than complete system failure. The ++api++ traverser in Plone is designed to handle API requests by parsing URL paths and routing them to appropriate endpoints, but when the same traverser identifier appears multiple times, the system enters a processing loop that becomes increasingly computationally expensive. This behavior creates a condition where legitimate API requests can be delayed or blocked, effectively reducing server responsiveness and potentially making the application unavailable to authorized users. The vulnerability is particularly concerning because it can be exploited through simple URL manipulation without requiring authentication, making it accessible to both authenticated and unauthenticated attackers.
The operational impact of this vulnerability extends beyond simple performance degradation to potentially compromise the availability and reliability of Plone applications that rely on RESTful API endpoints. Attackers can exploit this weakness by crafting malicious URLs with multiple ++api++ traversers, causing the server to consume excessive CPU cycles and memory resources. This resource exhaustion can lead to cascading failures where legitimate requests are delayed or rejected, affecting not only API functionality but potentially other system services that depend on the same resources. The vulnerability affects organizations running Plone systems in production environments where API availability is critical for content management operations and integration with external systems. Security practitioners should consider this issue when evaluating the attack surface of Plone applications, as it represents an easy-to-exploit vector for service disruption.
The mitigation strategy involves upgrading to patched versions of plone.rest, specifically versions 2.0.1 and 3.0.1, which contain fixes for the traverser handling logic. Organizations should also implement the suggested workaround of redirecting duplicate ++api++ URLs at the web server level, which can be accomplished through nginx or Apache configuration changes that redirect /++api++/++api++ paths to the single ++api++ endpoint. This approach provides immediate protection while longer-term upgrades are implemented. The vulnerability aligns with CWE-400, which covers resource exhaustion issues, and represents a specific instance of improper input validation where URL path components are not properly sanitized or handled. From an ATT&CK perspective, this vulnerability maps to the denial of service tactic, potentially enabling further exploitation through resource exhaustion that could be combined with other attack vectors to compromise system availability. Organizations should also consider implementing rate limiting and monitoring for unusual URL patterns to detect and prevent exploitation attempts. The fix addresses the root cause by ensuring that the traverser handles duplicate instances efficiently without exponential resource consumption, thereby maintaining system responsiveness under normal operational conditions.