Detect CVE-2026-48753: Incus S3 Multipart Upload Path Traversal Arbitrary File Write in IBM QRadar
Detects exploitation of CVE-2026-48753, a critical path traversal vulnerability (CVSS 9.9) in Incus (github.com/lxc/incus/v7/cmd/incusd) versions prior to 7.1.0. An attacker can write arbitrary files on the host by crafting malicious S3 multipart upload requests containing path traversal sequences in the object key, potentially leading to container escape, privilege escalation, or persistent backdoor installation.
MITRE ATT&CK
QRadar Detection Query
SELECT
DATEFORMAT(starttime, 'YYYY-MM-dd HH:mm:ss') AS event_time,
sourceip,
destinationip,
destinationport,
username,
"Process Name",
"File Path",
QIDNAME(qid) AS event_name,
logsourcename(logsourceid) AS log_source,
magnitude
FROM events
WHERE
LOGSOURCETYPENAME(devicetype) IN ('Linux Syslog', 'SentinelOne', 'CrowdStrike Falcon')
AND (
(
"Process Name" ILIKE '%incusd%'
AND (
UTF8(payload) ILIKE '%../%'
OR UTF8(payload) ILIKE '%2e%2e%2f%'
OR UTF8(payload) ILIKE '%2e%2e/%'
OR UTF8(payload) ILIKE '%252e252e%'
)
)
OR (
"Process Name" ILIKE '%incusd%'
AND "File Path" IS NOT NULL
AND "File Path" NOT ILIKE '/var/lib/incus/%'
AND "File Path" NOT ILIKE '/run/incus/%'
AND "File Path" NOT ILIKE '/tmp/%'
AND category = 18
)
)
AND LAST 24 HOURS
ORDER BY starttime DESC
LIMIT 1000QRadar AQL query detecting Incus path traversal exploitation through log source analysis looking for traversal sequences in incusd process context and file write events outside expected Incus storage paths.
Data Sources
Required Tables
False Positives & Tuning
- Incus backup or export operations that temporarily access non-standard file paths
- URL-encoded object keys in legitimate S3 API calls that match traversal signatures
- Monitoring agents reading Incus process memory or state from non-standard locations
- Development and testing environments running Incus with custom storage configurations
Other platforms for CVE-2026-48753
Testing Methodology
Validate this detection against 4 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 1CVE-2026-48753 PoC: Path Traversal via S3 Multipart Upload Initiation
Expected signal: Network log showing PUT/POST request to Incus S3 endpoint with URL-encoded path traversal sequence in the request URI; incusd process log entries showing the malformed object key
- Test 2CVE-2026-48753 Simulation: Anomalous File Write by Incusd Process
Expected signal: Linux audit log (auditd) syscall record showing openat/write to /etc/cron.d/ by process running as root; osquery file_events showing new file creation at sensitive path; EDR file creation alert for /etc/cron.d/
- Test 3CVE-2026-48753 Detection Validation: Incusd Version Audit
Expected signal: Process execution telemetry showing incus binary invoked with --version flag; no file modifications or network connections generated
- Test 4CVE-2026-48753 S3 Multipart Upload with Double-Encoded Traversal
Expected signal: Network request logs showing PUT to Incus S3 endpoint with %252e%252e and %2e%2e encoded sequences; incusd application logs recording the object key with encoded traversal characters before server-side decoding
Unlock Pro Content
Get the full detection package for CVE-2026-48753 including response playbook, investigation guide, and atomic red team tests.