Detect CVE-2026-48755: Incus Argument Injection in Backup Compression Algorithm (AFW/ACE) in Splunk
Detects exploitation of CVE-2026-48755, an argument injection vulnerability in Incus (github.com/lxc/incus/v7/cmd/incusd) versions prior to 7.2.0. The vulnerability exists in the backup compression algorithm selection, where unsanitized input is passed to compression utilities, enabling arbitrary file write (AFW) and arbitrary code execution (ACE) with incusd process privileges. An attacker with API access to the Incus daemon can inject shell metacharacters or additional arguments into the compression command, potentially achieving container escape or host compromise.
MITRE ATT&CK
SPL Detection Query
index=linux (sourcetype=syslog OR sourcetype=auditd OR sourcetype=osquery_results)
| where (process="incusd" OR parent_process="incusd" OR process_name="incusd")
OR (message LIKE "%incusd%" AND message LIKE "%compress%")
| eval suspicious_args=if(
match(cmdline, "[;&|`$()\\\\]") OR
match(cmdline, "--use-compress-program") OR
match(cmdline, "\.\.[\\/]") OR
match(cmdline, "--checkpoint-action") OR
match(cmdline, "-I\s"),
1, 0)
| where (process IN ("gzip", "bzip2", "xz", "zstd", "lz4", "tar", "pigz") AND parent_process="incusd")
OR suspicious_args=1
| table _time, host, user, process, parent_process, cmdline, message
| eval Technique="CVE-2026-48755 Incus Argument Injection"
| sort -_timeDetects incusd spawning compression utilities with injected arguments or shell metacharacters, and monitors for suspicious API-level backup requests containing argument injection payloads.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Legitimate administrative backup tasks passing custom compression programs through the Incus API
- Development environments testing Incus backup functionality with non-standard arguments
- Monitoring agents that parse Incus log output and trigger pattern matches on benign compression invocations
Other platforms for CVE-2026-48755
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 1Incus Backup Compression Argument Injection via API - File Write
Expected signal: Process event: incusd spawns gzip with command line containing '>' and '#' characters; file creation event at /tmp/pwned.txt by gzip process with parent incusd
- Test 2Incus Backup Compression Injection via tar --use-compress-program
Expected signal: Process chain: incusd -> tar with --use-compress-program argument; incusd -> sh -c with id command; file write to /tmp/id_output.txt
- Test 3Incus REST API Direct Backup Request with Injected Compression Algorithm
Expected signal: Incus API audit log entry for POST /1.0/instances/test-container/backups with compression_algorithm containing semicolon and redirect; gzip process spawned by incusd with injected shell command in arguments
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