CVE-2026-71805 in LZ-litchi
Summary
by MITRE • 09/09/2026
An arbitrary file upload and path traversal vulnerability exists in LZ-litchi 1.0.0. Unauthenticated remote attackers can upload arbitrary files and write them outside the intended storage directory via the directory parameter in POST /app-api/infra/file/upload.
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Analysis
by VulDB Data Team • 09/09/2026
The identified vulnerability represents a critical security flaw within version 1.0.0 of LZ-litchi, specifically affecting its file management subsystem. This issue is categorized as an arbitrary file upload combined with path traversal, allowing unauthenticated remote attackers to bypass intended access controls and write files to locations outside the designated storage directory. The root cause lies in the improper validation or sanitization of user-supplied input within the directory parameter used during POST requests directed at the /app-api/infra/file/upload endpoint. By manipulating this parameter with maliciously crafted path sequences, an attacker can redirect file writes to arbitrary system paths, effectively circumventing the application's sandboxing mechanisms and gaining unauthorized write access to sensitive areas of the server filesystem.
From a technical perspective, this vulnerability exploits weaknesses in how the backend processes relative or absolute path components provided by the client. Typically, such flaws arise when developers fail to normalize paths before processing them or do not strictly enforce allowlists for directory structures. In this specific instance, the application accepts the directory parameter without sufficiently stripping dangerous characters like dot-dot-slash sequences or resolving symbolic links that could lead outside the web root. This lack of rigorous input validation enables an attacker to construct a payload that traverses up the directory tree and places files in critical system directories, such as /etc, /tmp, or other locations where executable scripts can be executed by the server process or subsequently triggered via other application features.
The operational impact of this vulnerability is severe due to its unauthenticated nature and potential for remote code execution. Once an attacker successfully uploads a malicious file, typically in the form of a web shell such as PHP, JSP, or ASP script, they gain the ability to execute arbitrary commands on the underlying operating system with the privileges of the application server process. This can lead to complete compromise of the affected host, including data exfiltration, installation of persistent backdoors, lateral movement within the network, and denial of service through resource exhaustion. Since no authentication is required, automated scanning tools can easily discover and exploit this weakness across large networks, making it a high-risk target for opportunistic attacks and widespread botnet recruitment efforts.
This vulnerability aligns with CWE-434, which describes the unrestricted upload of files with dangerous types, as well as CWE-22, indicating improper limitation of a pathname to a restricted directory, commonly known as path traversal. In terms of offensive security frameworks, this exploit maps directly to MITRE ATT&CK technique T1505.003, which covers Server Component Web Shell installation. The attack vector involves the initial upload phase (T1106) followed by execution via the uploaded script (T1059). Defense in depth strategies are essential for mitigation. Immediate remediation requires updating LZ-litchi to a patched version that implements strict file type validation, enforces canonicalization of directory paths before processing, and restricts write operations strictly within an isolated upload directory using chroot or containerized environments where possible. Additionally, implementing Web Application Firewall rules to detect path traversal patterns in POST parameters can provide temporary protection while patches are applied.