Description

A path traversal vulnerability in LXD allows an attacker to achieve arbitrary host file read or unconstrained file creation. When processing image metadata templates, LXD fails to properly sanitize or restrict template file paths from escaping the instance templates directory (specifically affecting virtual machine / QEMU driver execution paths). An attacker can exploit this flaw by providing a crafted image archive with malicious template directives containing path traversal sequences, causing LXD to access or write files outside the intended template directory on the host system.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.5",
  "pubDate": "2026-08-12T21:17:35.880Z",
  "pubdate": "2026-08-12T21:17:35.880Z",
  "executiveSummary": "A path traversal vulnerability exists within LXD, specifically affecting the QEMU driver execution path when processing image metadata templates. The flaw arises from an inadequate sanitization and restriction mechanism applied to template file paths, permitting them to escape the designated instance templates directory.\nSuccessful exploitation of this security defect allows a malicious actor to achieve arbitrary host file read operations or unconstrained file creation capabilities. The primary impacted product is LXD, specifically targeting virtual machine execution pathways.\nThe risk implications are severe, as unauthorized reading or writing of arbitrary files on the host system compromises the confidentiality and integrity of the underlying host infrastructure.\nTo execute this attack, an adversary must supply a crafted image archive containing malicious template directives incorporating path traversal sequences. This forces LXD to process and interact with resources situated outside the intended administrative boundary.",
  "technicalDetails": "The root cause of the vulnerability is the lack of proper input sanitization and path validation when LXD handles image metadata templates. Specifically, the virtual machine and QEMU driver execution paths fail to enforce boundary checks, allowing relative path traversal sequences (such as dot-dot-slash) to bypass the intended instance templates directory constraints.\nThe vulnerable component resides in the LXD image metadata processing engine, which handles the parsing and extraction of template directives defined within image archives.\nThe attack vector requires an attacker to construct and provide a malicious image archive. Within this archive, the metadata templates contain crafted path traversal directives. When LXD processes the image metadata templates during instance setup or initialization, it evaluates the malicious paths without adequate validation.\nAs the parsing mechanism processes the archive, the traversal sequences force the application context to resolve file system operations outside the restricted template directory. Depending on the direction of the payload logic, this results in either reading sensitive host files and incorporating them into processing flows or writing arbitrary files directly to the host system.\nRegarding prerequisites and constraints, the attack exploits the image import or instantiation phase. Network exposure and authentication requirements depend on the specific LXD configuration, such as whether the remote API is exposed or if local image injection is utilized. The resulting post-exploitation impact includes complete host file system compromise, unauthorized data disclosure via arbitrary file reads, and potential persistence or system disruption via unconstrained file creation."
}