CVE-2026-113656 in apostrophe form
Summary
by MITRE • 10/20/2026
ApostropheCMS is an open-source Node.js content management system. Prior to 1.5.5 of the ApostropheCMS Form add-on, its form submission route stages unbounded multipart uploads before form validation or authentication and lacks upload size, count, and rate limits. Repeated unauthenticated submissions can consume temporary disk storage and disrupt form handling or other host services. This issue is fixed in ApostropheCMS Form 1.5.5.
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Analysis
by VulDB Data Team • 10/20/2026
ApostropheCMS is a widely used open-source content management system built on the Node.js runtime environment, designed to facilitate flexible website creation and maintenance. Within this ecosystem, the Form add-on serves as a critical component for handling user-generated data through web forms. However, in versions prior to 1.5.5 of this specific module, a significant architectural flaw exists within the request processing pipeline that exposes the underlying server infrastructure to resource exhaustion attacks. The core issue stems from the order of operations during form submission handling, where multipart file uploads are staged and written to temporary disk storage before any security checks or validation logic is executed.
The technical vulnerability arises because the application processes incoming multipart data immediately upon receipt, allocating disk space for uploaded files without first verifying the authenticity of the user or validating the integrity of the submitted data. This design decision means that unauthenticated actors can trigger substantial write operations to the server's temporary storage directory simply by sending HTTP POST requests with attached file payloads. The system lacks essential controls such as upload size limits, restrictions on the number of concurrent uploads per session, and rate limiting mechanisms for form submissions. Consequently, an attacker does not need valid credentials or complex exploit code; they only require the ability to send network packets containing multipart data to the vulnerable endpoint.
The operational impact of this flaw is primarily centered around Denial of Service through resource exhaustion. By repeatedly submitting forms with large files or a high volume of small files, an adversary can rapidly consume available disk space in the temporary directory where uploads are staged. This consumption leads to several detrimental outcomes for the hosting environment. First, it disrupts the normal functioning of form handling services, causing legitimate users' submissions to fail due to lack of storage space. Second, and more critically, if the server's root partition or designated temp drive fills up completely, it can cause broader system instability. Other applications running on the same host may fail to write logs, create temporary files, or operate correctly, leading to a cascading failure that affects multiple services rather than just the ApostropheCMS application itself.
This vulnerability aligns with CWE-400, which describes Uncontrolled Resource Consumption, as the system fails to limit the amount of resources an actor can consume during request processing. It also maps to MITRE ATT&CK technique T1496, Host File and Directory Enumeration or Resource Hijacking via Denial of Service, specifically in the context of resource exhaustion through unbounded input handling. The lack of authentication checks before file staging further exacerbates the risk by allowing anonymous actors to participate directly in this denial-of-service vector without any barrier to entry.
To mitigate this vulnerability, organizations running ApostropheCMS must upgrade the Form add-on to version 1.5.5 or later, where these architectural flaws have been addressed. In addition to upgrading, administrators should implement defense-in-depth strategies at the network and web server levels. Configuring reverse proxies such as Nginx or Apache to enforce strict limits on request body size can prevent excessively large uploads from reaching the application layer. Implementing rate limiting rules for form submission endpoints will also help mitigate rapid-fire attacks that attempt to exhaust resources through volume rather than file size. Furthermore, monitoring disk usage metrics and setting up alerts for abnormal spikes in temporary directory activity can provide early warning signs of such abuse attempts before they result in a full service outage.