Detect PrestaShop ps_facetedsearch PHP Object Injection Leading to Unauthenticated RCE (CVE-2026-54159) in Google Chronicle
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
YARA-L Detection Query
rule prestashop_facetedsearch_phpobjinjection_cve_2026_54159 {
meta:
author = "detection-engineering"
description = "Detects PHP Object Injection attempts against PrestaShop ps_facetedsearch module (CVE-2026-54159)"
severity = "CRITICAL"
cve = "CVE-2026-54159"
events:
$web.metadata.event_type = "NETWORK_HTTP"
$web.target.url = /.*ps_facetedsearch.*/ nocase
$web.network.http.method = "POST" or $web.network.http.method = "GET"
re.regex($web.target.url, `(O:\d+:\"|phar://|__wakeup|__destruct)`)
condition:
$web
}Chronicle YARA-L rule detecting HTTP requests to the PrestaShop ps_facetedsearch module URL that contain PHP serialized object markers or phar:// wrapper strings, indicative of CVE-2026-54159 exploitation.
Data Sources
Required Tables
False Positives & Tuning
- Benign clients whose encoded parameters coincidentally resemble serialization syntax
- Authorized security scanning traffic
- Log parsing artifacts duplicating URL fields
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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