Detect Incus exec-output Symlink Arbitrary File Write on Host (CVE-2026-48750) in Sumo Logic CSE
CVE-2026-48750 is a critical arbitrary file write vulnerability (CVSS 9.9) in Incus container/VM manager (github.com/lxc/incus/v7/cmd/incusd) versions prior to 7.2.0. A crafted container image can place a symlink at the exec-output path, causing incusd to write attacker-controlled content to arbitrary locations on the host filesystem. This enables container escape leading to full host compromise. A public PoC is available.
MITRE ATT&CK
Sumo Detection Query
_sourceCategory=linux/audit OR _sourceCategory=linux/syslog
| parse regex field=_raw "parent_process=(?P<parent_process>[^\s]+)"
| parse regex field=_raw "process=(?P<process>[^\s]+)"
| parse regex field=_raw "file_path=(?P<file_path>[^\s]+)"
| parse regex field=_raw "command=(?P<command>[^\n]+)"
| where (parent_process matches "*incusd*" OR parent_process matches "*incus*")
AND (
(file_path matches "/etc/*" OR file_path matches "/root/*" OR file_path matches "/var/spool/cron/*" OR file_path matches "/usr/local/bin/*" OR file_path matches "/lib/systemd/*")
OR (command matches "*exec-output*" OR command matches "*exec_output*")
)
| or (command matches "*exec-output*" AND (message matches "*symlink*" OR message matches "*lstat*"))
| fields _messageTime, _sourceHost, parent_process, process, file_path, command
| sort by _messageTime descSumo Logic query parsing Linux audit and syslog events to identify incusd-parented processes writing to sensitive host paths or referencing exec-output symlink indicators consistent with CVE-2026-48750.
Data Sources
False Positives & Tuning
- Standard incusd container management writing output to monitored host paths during normal operations
- Batch image deployment scripts using incus that reference exec-output paths legitimately
- Administrative maintenance tasks executed under incusd that touch sensitive system directories
Other platforms for CVE-2026-48750
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 symlink in exec-output path within container image
Expected signal: Auditd symlink syscall from process tree rooted at incusd; file write event to /etc/passwd path originating from incusd child process
- Test 2Detect symlink traversal via exec-output to /root/.ssh/authorized_keys
Expected signal: File write syscall to /root/.ssh/authorized_keys with incusd ancestor in process tree; auditd type=PATH record for authorized_keys
- Test 3Simulate exec-output symlink to systemd service unit for persistence
Expected signal: File creation event under /lib/systemd/system/ with incusd ancestor; subsequent systemd daemon-reload or service enable events
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