Detect PrestaShop ps_facetedsearch PHP Object Injection Leading to Unauthenticated RCE (CVE-2026-54159) in Splunk
CVE-2026-54159 is a critical (CVSS 10.0) PHP Object Injection vulnerability (CWE-74) in the PrestaShop ps_facetedsearch module (versions >=3.0.0, <4.0.4). The module caches faceted-search filter state using unsafe PHP deserialization of user-controllable input, allowing an unauthenticated attacker to submit a crafted serialized payload that instantiates gadget-chain objects, ultimately leading to arbitrary PHP code execution on the storefront web server. Exploitation requires no authentication and no user interaction, and a public PoC exists (GHSA-m5f5-28qr-9g9r).
MITRE ATT&CK
- Tactic
- Initial Access Execution Persistence
SPL Detection Query
index=web sourcetype=access_combined OR sourcetype=nginx:plus:access (uri_path="*ps_facetedsearch*" OR uri_query="*ps_facetedsearch*")
| eval decoded_query=urldecode(uri_query)
| rex field=decoded_query "(?<obj_marker>O:\d+:\\\"[A-Za-z0-9_\\\\]+\\\")"
| where isnotnull(obj_marker) OR match(decoded_query, "phar://") OR match(decoded_query, "__wakeup") OR match(decoded_query, "__destruct")
| stats count min(_time) as first_seen max(_time) as last_seen values(uri_path) as paths values(obj_marker) as markers by src_ip, http_user_agent
| sort -countSearches Splunk web access logs for POST/GET requests to the ps_facetedsearch module containing PHP serialized object markers or phar:// stream wrapper strings, indicating an attempted PHP Object Injection exploit against CVE-2026-54159.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Search engine crawlers submitting malformed but non-malicious query strings
- Internal vulnerability scanners testing the same endpoint
- Caching/CDN layer replaying query strings with encoded characters
Other platforms for CVE-2026-54159
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 1Simulate PHP Object Injection payload submission to ps_facetedsearch endpoint
Expected signal: Web server access log entry showing a POST to /module/ps_facetedsearch/ajax with a request body/query containing 'O:20:"PsFacetedSearchTest"' and 'phar://'.
- Test 2Simulate webshell drop artifact following simulated RCE
Expected signal: File creation event (via FIM/EDR/auditd) for a new .php file under the ps_facetedsearch cache directory, along with corresponding access log entries for the preceding exploitation request.
- Test 3Simulate malicious serialized payload with __destruct gadget marker
Expected signal: Proxy/web log entry capturing the POST request with URL-decoded body containing '__destruct' and '__wakeup' strings targeting the ps_facetedsearch endpoint.
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