CVE-2026-27933 is a vulnerability classified under CWE-613 (Insufficient Session Expiration) affecting manyfold, an open-source, self-hosted web application designed for managing collections of 3D models with a focus on 3D printing workflows. Versions prior to 0.133.0 do not adequately expire or protect session cookies, leading to the risk of session hijacking via cookie leakage through proxy caches. Proxy caches, commonly used to improve web performance, may inadvertently store and serve session cookies to unauthorized parties if not properly configured. An attacker who can access these proxy caches or intercept cached responses may retrieve valid session cookies, allowing them to impersonate legitimate users without authentication. The CVSS v3.1 score of 6.8 reflects a medium severity, with attack vector being network-based, requiring high attack complexity, no privileges, and user interaction. The vulnerability impacts confidentiality and integrity by enabling unauthorized access to user sessions but does not affect availability. The issue was addressed in version 0.133.0 by improving session expiration and cookie handling to prevent leakage through caching mechanisms. No public exploits have been reported yet, but the risk remains for organizations running outdated versions, especially those exposing manyfold instances to the internet or using proxy caches without proper security controls.

The primary impact of this vulnerability is unauthorized access to user sessions, which compromises confidentiality and integrity of sensitive data managed within manyfold, such as proprietary 3D models and design files. Attackers gaining session control can manipulate or exfiltrate 3D model data, potentially causing intellectual property theft or sabotage. Since manyfold is self-hosted, organizations with publicly accessible instances are at risk, particularly if proxy caches are misconfigured. The vulnerability does not affect system availability directly but can lead to significant operational and reputational damage if exploited. Industries relying on 3D printing for prototyping, manufacturing, or design—such as aerospace, automotive, healthcare, and consumer electronics—may face increased risk due to the sensitive nature of their 3D assets. The medium severity score indicates a moderate threat level, but the requirement for user interaction and high attack complexity somewhat limits widespread exploitation. Nonetheless, organizations ignoring this vulnerability risk targeted attacks and data breaches.

Organizations should immediately upgrade manyfold installations to version 0.133.0 or later, where the vulnerability is fixed. Additionally, administrators must audit and configure proxy caches to ensure they do not store or serve session cookies; this includes setting appropriate Cache-Control headers (e.g., no-store, private) and validating cache behavior. Implementing secure cookie attributes such as HttpOnly, Secure, and SameSite can further reduce cookie exposure. Regularly reviewing session management policies to enforce short session lifetimes and automatic expiration after inactivity is critical. Network segmentation and limiting access to manyfold instances reduce exposure. Monitoring web traffic for anomalous session activity and employing web application firewalls (WAFs) with rules to detect session hijacking attempts can provide additional defense layers. Finally, educating users about phishing and social engineering risks helps mitigate the user interaction requirement for exploitation.