CVE-2026-23835 is a vulnerability classified under CWE-73 (External Control of File Name or Path) found in the open-source human-and-AI-agent network platform LobeHub, specifically in its lobe-chat product. Versions prior to 1.143.3 contain a flaw in the file upload feature located in the Knowledge Base > File Upload section. The vulnerability arises because the system does not validate the integrity of upload requests, allowing an attacker to intercept and modify parameters such as the file path and size. This manipulation enables the creation of arbitrary files in abnormal or unintended directories, potentially leading to unauthorized file placement or overwriting. Furthermore, the system relies on the client-supplied size parameter to enforce monthly upload quotas. By falsifying this value, an attacker can upload files that exceed quota limits without detection, causing resource exhaustion. The consequences include direct financial losses due to billing discrepancies, degraded service availability (failed uploads, delayed content delivery, or temporary suspension of upload functionality), and indirect denial of service affecting other users sharing the same subscription. Additionally, the excessive uploads can distort monitoring metrics and overload downstream systems like backups, malware scanning, and media processing pipelines, undermining overall operational stability. The vulnerability does not require user interaction but does require the ability to upload files, implying some level of authenticated access. The issue was patched in version 1.143.3, which validates upload requests properly to prevent parameter tampering.

For European organizations using lobehub's lobe-chat platform, this vulnerability poses several risks. Financially, operators may incur unexpected costs due to manipulated upload sizes bypassing quota enforcement, leading to overuse of storage and bandwidth without corresponding billing. Operationally, exhaustion of storage and processing resources can degrade service availability, impacting business continuity and user experience. Indirect denial of service can affect multiple users or projects under shared subscription plans, potentially disrupting collaborative workflows. The distortion of monitoring data and overload of backend systems can hinder incident detection and response capabilities, increasing the risk of unnoticed malicious activity or system failures. Organizations relying on lobe-chat for knowledge management or AI-agent collaboration may face interruptions or data integrity issues. Given the open-source nature and potential for deployment in diverse environments, the threat could affect sectors ranging from academia to enterprises leveraging AI collaboration tools. The lack of known exploits in the wild reduces immediate risk but does not eliminate the need for prompt remediation.

European organizations should immediately upgrade lobe-chat to version 1.143.3 or later to apply the official patch. Beyond patching, implement strict validation and sanitization of all file upload parameters on the server side to prevent tampering. Employ robust access controls to restrict upload capabilities to trusted users and monitor upload activities for anomalies such as unusual file paths or size discrepancies. Integrate quota enforcement mechanisms that rely on server-side calculations rather than client-supplied data to prevent quota bypass. Deploy file integrity monitoring and alerting systems to detect unauthorized file creations or modifications. Regularly audit storage usage and backup processes to identify abnormal consumption patterns. Consider isolating upload directories with strict permissions and sandboxing to limit the impact of arbitrary file writes. Enhance logging and monitoring of upload-related events to facilitate rapid detection and response. Finally, educate users and administrators about the risks of manipulating upload parameters and encourage prompt reporting of suspicious behavior.