Description

A link following vulnerability in LXD allows an attacker to achieve root command execution on the host system. During the import or unpacking of crafted image or backup archives, LXD fails to properly validate and confine the backup.yaml file when it exists as a symbolic link. An attacker can exploit this flaw by providing a malicious archive with a symlinked backup.yaml file, causing LXD to process unconfined configuration metadata and execute arbitrary commands with root privileges.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.9",
  "pubDate": "2026-08-12T20:17:47.187Z",
  "pubdate": "2026-08-12T20:17:47.187Z",
  "executiveSummary": "A link following vulnerability exists in LXD during the import or unpacking of crafted image or backup archives, resulting in root command execution on the host system. The vulnerability stems from the failure of LXD to properly validate and confine the backup.yaml file when it exists as a symbolic link.\nThis flaw allows an attacker to achieve full root-level compromise of the host system by supplying a malicious archive containing a symlinked backup.yaml file. Upon processing the archive, LXD evaluates unconfined configuration metadata, leading to arbitrary command execution with elevated privileges.\nThe affected product is LXD. The risk implications are severe, as successful exploitation results in complete host compromise and arbitrary code execution as the root user. Attacker capabilities require the ability to supply a malicious image or backup archive to the target system for processing.",
  "technicalDetails": "The vulnerability resides in the archive import and unpacking mechanism of LXD, specifically within the handling of the backup.yaml configuration file. The root cause is improper path validation and lack of confinement when processing extracted file elements, failing to adequately check if target configuration files are symbolic links pointing to sensitive system locations or unconfined paths.\nExploitation occurs when an attacker crafts a malicious archive, such as an image or backup file, in which the expected backup.yaml metadata file is replaced by a symbolic link. When the LXD daemon processes, unpacks, or reads this archive, it blindly follows the symbolic link without restricting operations to the intended extraction directory or verifying the file's integrity and provenance.\nThe attack flow proceeds as follows: First, the attacker generates a malicious archive embedding a symbolic link targeting backup.yaml. Second, the attacker induces the LXD system to import or unpack this archive. Third, LXD traverses the symbolic link during the parsing of configuration metadata. Fourth, LXD processes the unconfined configuration parameters dictated by the attacker via the linked structure. Finally, this evaluation triggers arbitrary command execution running under the security context of the root-privileged LXD daemon.\nThe vulnerable component is the archive ingestion and extraction routine responsible for parsing backup.yaml. Authentication and privilege requirements depend on the specific vector used to ingest the malicious archive, but successful exploitation culminates in root-level execution on the host. The attack vector requires the processing of untrusted archives by the LXD service."
}