Detect CVE-2026-48753: Incus S3 Multipart Upload Path Traversal Arbitrary File Write in Google Chronicle
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
YARA-L Detection Query
rule cve_2026_48753_incus_path_traversal {
meta:
author = "df00tech Detection Platform"
description = "Detects CVE-2026-48753 Incus S3 multipart upload path traversal exploitation"
severity = "CRITICAL"
priority = "HIGH"
reference = "https://github.com/lxc/incus/security/advisories/GHSA-ccjc-4qc3-jxqc"
cve = "CVE-2026-48753"
created = "2026-06-27"
events:
$e.metadata.event_type = "PROCESS_LAUNCH" OR
$e.metadata.event_type = "FILE_CREATION" OR
$e.metadata.event_type = "NETWORK_HTTP"
$e.principal.process.file.full_path = /incusd$/
(
$e.network.http.request.url = /(\.\.\/|%2e%2e%2f|%2e%2e\/|%252e%252e)/i OR
(
$e.target.file.full_path != "/var/lib/incus/" AND
$e.metadata.event_type = "FILE_CREATION"
)
)
condition:
$e
}Chronicle YARA-L rule detecting Incus process activity with path traversal patterns in HTTP requests or file creation events outside the expected Incus storage directory.
Data Sources
Required Tables
False Positives & Tuning
- Incus instances with non-standard installation paths not under /var/lib/incus
- Legitimate S3 API calls to object storage backends with URL-encoded special characters
- Incus upgrade processes that temporarily write files during migration to new versions
- Authorized security testing using known PoC patterns against isolated Incus test environments
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
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