Description

Incus is a system container and virtual machine manager. Prior to version 7.2.0, an arbitrary file write exists in the Incus client when a malicious image server returns a crafted `Incus-Image-Hash` header. This can lead to arbitrary command execution as root on the server. Version 7.2.0 patches the issue.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.9",
  "pubDate": "2026-08-21T15:16:41.347Z",
  "pubdate": "2026-08-21T15:16:41.347Z",
  "executiveSummary": "An arbitrary file write vulnerability exists in the Incus client prior to version 7.2.0, caused by improper handling of responses from a malicious image server. An attacker operating a compromised or malicious image server can supply a crafted Incus-Image-Hash header, allowing them to write arbitrary files to the filesystem.\nThis vulnerability impacts the Incus system container and virtual machine manager. Successful exploitation can lead to arbitrary command execution as root on the server, presenting severe risk implications regarding host integrity and complete system compromise.\nAttacker capabilities require the ability to act as or control a remote image server interacting with the Incus client. Exploitation requirements rely on the client initiating an operation that communicates with the malicious server and processes the crafted response headers without adequate sanitization or validation.",
  "technicalDetails": "The vulnerability resides in the Incus client component responsible for processing responses received from remote image servers. Specifically, the client fails to properly validate and sanitize the Incus-Image-Hash header returned during image retrieval or interaction operations.\nThe root cause is an insecure file write primitive facilitated by trusting untrusted input derived from HTTP response headers. When the Incus client processes the malicious Incus-Image-Hash header containing directory traversal sequences or absolute paths, it writes incoming data to arbitrary locations on the host filesystem.\nThe attack flow proceeds as follows: First, a user or automated process using the Incus client connects to a malicious image server. Second, the malicious server responds to an image-related request containing a crafted Incus-Image-Hash header. Third, the vulnerable Incus client parses the response and writes the payload to an arbitrary file path specified by the header.\nBecause the Incus client or associated daemon operations frequently execute with elevated privileges, this arbitrary file write can be leveraged to overwrite critical system configuration files, binaries, or startup scripts. Consequently, subsequent execution of these components results in arbitrary command execution as root on the server.\nThe vulnerability affects Incus client versions prior to 7.2.0. Authentication requirements depend on the configuration of the image repository, but exploitation generally requires the client to voluntarily interact with the untrusted or malicious image server endpoint."
}