CVE-2026-82235 in Filebrowser
Summary
by MITRE • 08/28/2026
filebrowser through 2.63.23 fails to validate named pipes in directory archive and public download handlers, allowing attackers to trigger blocking open syscalls. Authenticated users or anonymous visitors with public share links can repeatedly request archives containing named pipes to pin server goroutines and exhaust connection resources.
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Analysis
by VulDB Data Team • 08/28/2026
The vulnerability identified in FileBrowser versions up to 2.63.23 represents a significant resource exhaustion flaw rooted in the improper handling of special file types within archive generation and public download mechanisms. Specifically, the application fails to validate or sanitize named pipes, also known as FIFOs, when they are included in directories targeted for archiving or direct downloading. This oversight allows an attacker who has authenticated access to the FileBrowser instance, or even anonymous users with valid links to publicly shared folders containing such files, to exploit this behavior by repeatedly requesting archives that include these named pipe entries. The core technical flaw lies in the server's attempt to open and read from these special file descriptors without appropriate checks for their type, leading directly to a denial of service condition rather than data exfiltration or remote code execution.
From an operational perspective, when the FileBrowser backend attempts to process a directory containing named pipes for archive creation, it invokes system calls such as open() on each entry within that directory structure. Unlike regular files where read operations return data and eventually reach end-of-file status allowing the connection to close gracefully, opening a named pipe causes the calling thread or goroutine in Go-based applications like FileBrowser to block indefinitely until another process opens the other end of the pipe for writing. Since the server-side handler does not implement timeouts or non-blocking I/O strategies specifically tailored for special file types during this extraction phase, each request containing such a pipe pins a server goroutine permanently. This results in a gradual but steady consumption of available connection resources and memory associated with those blocked threads.
The impact of this vulnerability is primarily a denial of service against the FileBrowser infrastructure. As attackers send repeated requests for archives or downloads involving directories populated with named pipes, the number of pinned goroutines increases linearly with each request until the server exhausts its thread pool or connection limits. This effectively renders the application unresponsive to legitimate users who are attempting to access files through normal means. The severity is exacerbated by the fact that authentication may not be required if public shares containing such malicious directory structures exist, allowing any internet user on the network path to contribute to the resource exhaustion attack vector without needing valid credentials.
This issue aligns with CWE-400, which describes Uncontrolled Resource Consumption, as the application fails to limit or monitor the resources consumed by processing specific input types that lead to blocking operations. Furthermore, in terms of tactical classification within the MITRE ATT&CK framework, this vulnerability facilitates resource hijacking and denial of service capabilities, often categorized under techniques related to impact or availability disruption rather than initial access or persistence. The attack vector leverages standard HTTP GET requests for downloads or archive generation endpoints, making it difficult to distinguish from legitimate traffic without deep packet inspection or specific behavioral monitoring tools that track goroutine states and blocking system calls on the host operating system.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. The most effective solution is to upgrade FileBrowser to a version later than 2.63.23 where this validation logic has been corrected to explicitly check for special file types such as named pipes, symbolic links pointing to non-existent targets, or other device files before attempting to include them in archive streams. For environments where immediate upgrading is not feasible, administrators should implement strict access controls on directories that might contain user-uploaded archives and consider deploying a Web Application Firewall rule set designed to detect patterns of repeated large download requests from single sources. Additionally, configuring the underlying Go runtime or reverse proxy layers with aggressive timeout settings for long-running operations can help mitigate the duration of blocked goroutines, although this is less effective than patching the root cause in the application code itself. Regular auditing of uploaded content and restricting user permissions to prevent the creation of special file types within shared directories also serves as a robust preventive measure against exploitation attempts.