Detect CVE-2023-27351 - PaperCut NG/MF Improper Authentication Exploitation in Google Chronicle
Detects exploitation attempts targeting CVE-2023-27351, an improper authentication vulnerability (CWE-287) in PaperCut NG/MF print management software. This CISA KEV-listed vulnerability allows unauthenticated attackers to bypass authentication controls, potentially enabling unauthorized access to the PaperCut administration interface and sensitive print management data. Threat actors have actively exploited PaperCut vulnerabilities in the wild for initial access and lateral movement.
MITRE ATT&CK
YARA-L Detection Query
rule cve_2023_27351_papercut_auth_bypass {
meta:
author = "df00tech Detection Engineering"
description = "Detects CVE-2023-27351 PaperCut NG/MF improper authentication exploitation attempts"
severity = "HIGH"
priority = "HIGH"
reference = "https://www.papercut.com/kb/Main/PO-1216-and-PO-1219"
cve = "CVE-2023-27351"
events:
$http.metadata.event_type = "NETWORK_HTTP"
$http.network.http.method = /POST|GET/
$http.network.http.response_code in (200, 302)
$http.target.port in (9191, 9192)
(
$http.network.http.request_url = /\/rpc\/api\/json/
or $http.network.http.request_url = /\/app\?service=/
or $http.network.http.request_url = /\/health-check/
or $http.network.http.request_url = /\/app\/admin/
)
not $http.principal.user.userid = /admin|papercut|svc_/
match:
$http.principal.ip over 5m
outcome:
$risk_score = max(
if($http.network.http.method = "POST" and $http.network.http.response_code = 200, 80, 50)
)
$request_count = count_distinct($http.network.http.request_url)
condition:
#http >= 1
}Chronicle YARA-L rule detecting HTTP requests to PaperCut NG/MF management endpoints on standard ports with successful response codes from non-administrative user contexts, indicating potential CVE-2023-27351 exploitation.
Data Sources
Required Tables
False Positives & Tuning
- PaperCut service accounts performing automated management tasks
- Internal health monitoring systems with unrecognized user identifiers
- Authorized security testing and red team exercises
Other platforms for CVE-2023-27351
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-2023-27351 Unauthenticated Health Check Probe
Expected signal: HTTP GET request to /health-check and /api/health on port 9191 from test host IP, HTTP 200 response in web server logs.
- Test 2CVE-2023-27351 Unauthenticated RPC API Call
Expected signal: POST request to /rpc/api/json on port 9191 with Content-Type: application/json header, HTTP 200 response with JSON body in web server logs if vulnerable.
- Test 3CVE-2023-27351 Admin Setup Page Access Attempt
Expected signal: GET request to /app with query parameter service=page/SetupCompleted on port 9191, HTTP response code logged in IIS or PaperCut access logs.
- Test 4CVE-2023-27351 Rapid Sequential Endpoint Enumeration
Expected signal: Multiple sequential HTTP requests to PaperCut endpoints within a short timeframe from a single source IP, visible in web server access logs with timestamps.
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