Detect Incus Arbitrary File Read/Write via Malicious Image Template Symlink in Splunk
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
SPL Detection Query
index=os OR index=auditd OR index=syslog
(source="/var/log/syslog" OR source="/var/log/daemon.log" OR sourcetype="linux_audit")
(
(process_name="incusd" OR process_name="incus")
AND (
(message="*templates/*" AND (message="*symlink*" OR message="*readlink*" OR message="*lstat*"))
OR (message="*path escape*" OR message="*container image*" OR message="*chroot escape*")
OR (file_path="*/var/lib/incus/images/*" AND (message="*../../../*" OR message="*..\\..\\*"))
)
)
OR (
sourcetype="linux_audit"
AND syscall IN ("readlink", "lstat", "open", "openat", "symlinkat")
AND exe="*/incusd"
AND (key="container_escape" OR filepath="*templates/*")
)
| eval alert_name="CVE-2026-48752 - Incus Template Symlink Traversal"
| eval severity="critical"
| table _time, host, process_name, file_path, message, syscall, exe, alert_name, severity
| sort -_timeSplunk detection for CVE-2026-48752 targeting incusd process activity involving symlink operations within Incus template directories and potential path traversal artifacts in OS and auditd logs.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Legitimate Incus image maintenance operations involving template directory access
- Custom Incus image build pipelines that use symlinks within templates/ for valid configuration purposes
- Administrative scripts that introspect Incus image stores for inventory or backup purposes
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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