Detect Incus Arbitrary File Read/Write via Malicious Image Template Symlink in Elastic Security
CVE-2026-48752 is a critical vulnerability (CVSS 9.9) in Incus (github.com/lxc/incus/v7/cmd/incusd) versions prior to 7.2.0. A malicious container image can include a crafted symlink within the templates/ directory that, when processed by incusd during image import or container creation, allows an attacker to read or write arbitrary files on the host filesystem. This constitutes a container escape primitive with host takeover potential. A public proof-of-concept exists.
MITRE ATT&CK
Elastic Detection Query
sequence by host.name with maxspan=5m
[process where process.name == "incusd" and
(
process.args : ["*templates/*", "*image import*", "*container create*"]
)
] by process.pid
[file where process.name == "incusd" and
(
file.path : ["/var/lib/incus/*", "/var/snap/incus/*"] and
(
file.path : ["*../../../*", "*templates/../*"] or
file.Ext.original.path : ["*templates/*"]
)
) or
(
event.category == "file" and
event.type == "creation" and
file.path : ["/etc/*", "/root/*", "/home/*", "/proc/*"] and
process.name == "incusd"
)
] by process.pidElastic EQL sequence detection correlating incusd process execution with suspicious file operations outside expected container boundaries or within host-sensitive directories.
Data Sources
Required Tables
False Positives & Tuning
- Incus daemon legitimate host file access during container initialisation for kernel module loading
- Monitoring agents reading Incus image store for asset inventory
- Backup tooling accessing /var/lib/incus directories during scheduled jobs
Other platforms for CVE-2026-48752
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Create Malicious Incus Image with Template Symlink Pointing to /etc/passwd
Expected signal: incusd process accessing /etc/passwd via symlink resolution from templates/ directory; auditd SYSCALL records for readlink/open by incusd PID targeting /etc/passwd
- Test 2Exploit Incus Template Symlink for Arbitrary Host File Write
Expected signal: incusd creating or writing to /tmp/incus-host-write-target via symlink from templates/; FileWriteInfo events for incusd outside container directories
- Test 3Scan Incus Image Store for Existing Malicious Template Symlinks
Expected signal: Read-only filesystem traversal of /var/lib/incus/images by the scanning shell process; no incusd involvement expected
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