Detect Incus exec-output Symlink Arbitrary File Write on Host (CVE-2026-48750) in Google Chronicle
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
YARA-L Detection Query
rule incus_exec_output_symlink_host_write {
meta:
author = "df00tech Detection Engineering"
description = "Detects CVE-2026-48750: Incus exec-output symlink arbitrary file write on host"
severity = "CRITICAL"
priority = "HIGH"
reference = "https://github.com/lxc/incus/security/advisories/GHSA-73hr-m85f-64v9"
events:
(
$e1.metadata.event_type = "PROCESS_LAUNCH"
AND (
re.regex($e1.principal.process.parent_process.file.full_path, `(incusd|incus)$`)
)
AND (
re.regex($e1.target.process.command_line, `exec.output|exec_output`)
OR re.regex($e1.target.file.full_path, `^/(etc|root|var/spool/cron|usr/local/bin|lib/systemd)/`)
)
)
OR
(
$e1.metadata.event_type = "FILE_CREATION"
AND re.regex($e1.principal.process.parent_process.file.full_path, `(incusd|incus)$`)
AND re.regex($e1.target.file.full_path, `^/(etc|root|var/spool/cron|usr/local/bin|lib/systemd|home/[^/]+/\.ssh)/`)
)
condition:
$e1
}Chronicle YARA-L rule detecting incusd-parented process launches referencing exec-output paths and file creation events to sensitive host directories, indicating CVE-2026-48750 exploitation.
Data Sources
Required Tables
False Positives & Tuning
- Authorized incus container lifecycle management creating files in system directories
- Legitimate image build automation referencing exec-output in command lines
- Infrastructure provisioning tooling running under incusd that touches standard system paths
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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