Description

Incus is a system container and virtual machine manager. Prior to version 7.1.0, the S3 protocol upload endpoint is vulnerable to path traversal and allows creation of arbitrary files on the host. This behavior could lead to arbitrary command execution. Version 7.1.0 fixes the issue.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.9",
  "pubDate": "2026-08-21T15:16:40.800Z",
  "pubdate": "2026-08-21T15:16:40.800Z",
  "executiveSummary": "An unauthenticated path traversal vulnerability exists within the S3 protocol upload endpoint of Incus prior to version 7.1.0. This critical flaw allows remote attackers to bypass path sanitization mechanisms and perform arbitrary file creation on the host operating system.\nThe vulnerability directly impacts the system container and virtual machine manager, specifically undermining host isolation guarantees. By leveraging the S3 protocol upload mechanism, an adversary with network access to the endpoint can write arbitrary files to restricted locations across the underlying host filesystem.\nThe risk implications are severe, as arbitrary file creation on a container management host frequently escalates to arbitrary command execution through manipulation of system binaries, configuration files, or initialization scripts. Exploitation requires network reachability to the vulnerable S3 protocol upload endpoint exposed by the affected Incus service.\nRemediation requires upgrading the Incus software to version 7.1.0 or later, which contains the necessary input validation fixes to properly neutralize path traversal vectors within the S3 handling logic.",
  "technicalDetails": "The root cause of the vulnerability stems from insufficient validation and sanitization of user-supplied filenames or object keys provided during the S3 protocol upload process. The vulnerable component is the S3 protocol upload endpoint within Incus, which fails to adequately restrict directory traversal sequences such as dot-dot-slash patterns.\nAffected versions include all releases of Incus prior to version 7.1.0. The vulnerability is accessible via the network where the S3 protocol upload endpoint is exposed. Depending on the configuration, the attack may be conducted without prior authentication or valid credentials if the endpoint permits anonymous or unauthenticated ingestion.\nThe step-by-step attack flow begins when an attacker crafts a malicious S3 API upload request containing path traversal sequences (e.g., ../../../) embedded within the target object name or file path parameters. Upon receiving this payload, the vulnerable S3 endpoint processes the request without validating whether the resolved destination path remains strictly contained within the intended storage directory.\nBecause of this lack of boundary enforcement, the application writes the uploaded payload data directly to the attacker-specified absolute or relative path on the host filesystem. The payload behavior allows an attacker to overwrite existing system files or plant new files in sensitive directories.\nThe post-exploitation impact is profound. By weaponizing the arbitrary file creation capability, an attacker can overwrite critical system binaries, inject malicious cron jobs, manipulate authorized SSH keys, or alter service configuration files. This ultimately leads to arbitrary command execution on the host system, compromising the entire Incus management environment and any hosted system containers or virtual machines."
}