CVE-2026-55168 in Runtipi
Summary
by MITRE • 08/22/2026
Runtipi is a personal homeserver orchestrator. In 4.10.0 and earlier, Runtipi accepts symbolic links from an attacker-controlled backup archive and copies them into live application paths during the backup restore flow. An authenticated attacker can plant user-config/app.env as a symlink to an arbitrary reachable path and then send PUT /api/user-config/demoapp3:_user with attacker-controlled appEnv content. FilesystemService.writeTextFile() follows the planted link, allowing content to be written outside the intended restore and user-config directory boundary with Runtipi process permissions. This issue is fixed in version 4.10.1.
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Analysis
by VulDB Data Team • 08/22/2026
Runtipi serves as a personal homeserver orchestrator designed to simplify the deployment and management of self-hosted applications. A critical security vulnerability was identified within versions up to 4.10.0, specifically affecting the backup restore functionality and user configuration endpoints. The core issue stems from insufficient validation of file paths during archive extraction processes. When an authenticated attacker provides a maliciously crafted backup archive containing symbolic links pointing to arbitrary locations on the filesystem, the system fails to detect or restrict these references. During the restoration flow, Runtipi blindly follows these symbolic links and copies their targets into live application directories without verifying that the destination resides within expected boundaries.
The technical flaw is rooted in how the FilesystemService.writeTextFile() method handles input data derived from user-controlled archives. By planting a file such as user-config/app.env as a symlink to an arbitrary reachable path, an attacker can manipulate where subsequent write operations occur. This mechanism allows for writing content outside the intended restore directory and beyond the confines of the user-config folder. Because these operations are executed with the permissions of the Runtipi process, the impact extends significantly beyond simple data corruption or unauthorized reading. The ability to write arbitrary files in locations accessible by the service account can lead to remote code execution if configuration files containing executable logic are overwritten, or it may facilitate privilege escalation through manipulation of system-level configurations.
From an operational perspective, this vulnerability enables a authenticated attacker to achieve path traversal and arbitrary file writes within the context of the Runtipi process. This aligns with CWE-22 Improper Limitation of a Pathname to a Restricted Directory, as the application fails to enforce strict directory boundaries during archive extraction. Furthermore, the exploitation technique involves manipulating input data to influence system resource usage in an unintended manner, which maps to ATT&CK T1564.008 Hidden Files and Directories if used for persistence or evasion, though primarily it represents a severe integrity violation allowing unauthorized modification of critical application files. The severity is heightened by the fact that authentication alone is sufficient to trigger this behavior, lowering the barrier for exploitation compared to unauthenticated attacks.
Mitigation strategies must prioritize immediate version upgrades as the primary defense vector. Runtipi has addressed this issue in version 4.10.1 and later releases by implementing stricter validation checks on symbolic links during archive restoration. Administrators should ensure that all instances of Runtipi are updated to patched versions where path canonicalization is enforced before any file system operations occur. Additionally, running the application with minimal necessary privileges can reduce the blast radius if such vulnerabilities exist in other components. Input sanitization practices should also be reviewed to ensure that symbolic links from external sources are either rejected outright or resolved safely within a designated sandboxed directory structure. Regular auditing of backup archives and restricting upload permissions for untrusted users further mitigates the risk associated with archive-based attacks.