Detect CVE-2026-48749: Incus Arbitrary File Read/Write via rootfs Symlink in Malicious Image in CrowdStrike LogScale
Detects exploitation of CVE-2026-48749, a critical vulnerability in Incus (github.com/lxc/incus/v7/cmd/incusd) versions prior to 7.2.0. Attackers can craft a malicious container image with symlinks in the rootfs/ directory that resolve to host filesystem paths, enabling arbitrary file read and write on the underlying host. This constitutes a container escape primitive and may lead to full host compromise. CVSS 9.9 with public PoC available.
MITRE ATT&CK
LogScale Detection Query
// CVE-2026-48749: Incus rootfs symlink escape detection
#event_simpleName IN (FileWritten, FileCreated, FileDeleted, SymlinkCreated)
| ImageFileName = /incusd|incus/i
| TargetFileName = /\/var\/lib\/incus\/.*\/rootfs\//
| eval phase="rootfs_activity"
| union (
#event_simpleName IN (FileOpenInfo, FileWritten)
| ImageFileName = /incusd|incusd/i
| TargetFileName = /\/etc\/passwd|\/etc\/shadow|\/root\/.ssh|\/etc\/sudoers|\/etc\/crontab/
| eval phase="host_file_access"
)
| groupBy([ComputerName, UserName, ImageFileName], function=[
count(as=event_count),
collect(TargetFileName, as=target_files),
collect(phase, as=phases)
])
| where array:count(phases) >= 1
| sort event_count desc
| eval cve="CVE-2026-48749"
| eval risk=if(array:contains(phases, "host_file_access"), "CRITICAL", "HIGH")CrowdStrike Falcon Next-Gen SIEM query detecting incusd process creation and modification of rootfs symlink paths alongside host sensitive file access patterns associated with CVE-2026-48749.
Data Sources
Required Tables
False Positives & Tuning
- Authorized Incus image import and launch workflows in development environments
- Container storage defragmentation or optimization tools accessing rootfs directories
- Incus daemon recovery processes after unclean shutdown accessing both rootfs and host paths
- Automated vulnerability scanning of container environments with read access to host files
Other platforms for CVE-2026-48749
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 rootfs symlink targeting /etc/passwd
Expected signal: auditd syscall events for symlink() within /var/lib/incus/*/rootfs/; file open events on host /etc/passwd initiated by incusd process; DeviceFileEvents showing incusd accessing /etc/passwd outside container namespace
- Test 2Exploit rootfs symlink for host SSH authorized_keys write
Expected signal: File write event on host /root/.ssh/authorized_keys attributed to incusd or container init process; auditd records showing write() syscall to /root/.ssh/authorized_keys from incusd context; FIM alert on /root/.ssh/authorized_keys modification
- Test 3Read host /etc/shadow via rootfs symlink for credential harvesting
Expected signal: File read event on host /etc/shadow initiated by incusd process context; auditd openat() syscall on /etc/shadow attributed to container namespace but resolved to host inode; audit log entry for privileged file access outside expected paths
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