Output Messenger Directory Traversal and Arbitrary File Access Vulnerability (CVE-2025-27920) Security Advisory
Executive & SecOps Summary
SECOPS ASSESSMENTOutput Messenger versions prior to 2.0.63
Authenticated attackers can leverage directory traversal sequences ('../') to access sensitive configuration files and arbitrary system files, potentially leading to remote code execution (RCE)
Immediately upgrade Output Messenger to the latest secure version (2.0.63 or higher) and restrict network access
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Administrators must immediately upgrade Output Messenger to version 2.0.63 or higher. For Windows-based server environments, use the following PowerShell commands to stop the service, download the latest installer, and perform a silent upgrade.
# Stop the Output Messenger service
Stop-Service -Name 'OutputMessengerServer' -Force -ErrorAction SilentlyContinue
# Download and silently install the latest secure version (2.0.63+)
$url = 'https://www.outputmessenger.com/downloads/outputmessengerserver.exe'
$outpath = '$env:TEMP\outputmessengerserver.exe'
Invoke-WebRequest -Uri $url -OutFile $outpath
Start-Process -FilePath $outpath -ArgumentList '/S' -Wait
# Restart the service and verify status
Start-Service -Name 'OutputMessengerServer'
Get-Service -Name 'OutputMessengerServer'2. Temporary Workaround & Hardening Configuration
If an immediate patch is not feasible, restrict access to the Output Messenger ports (default: 14121, 14122, 14124) using firewall rules, allowing connections only from trusted internal networks or VPNs.
# Example iptables rules to restrict Output Messenger ports to internal subnet 10.0.0.0/8
iptables -A INPUT -p tcp -s 10.0.0.0/8 --dport 14121:14124 -j ACCEPT
iptables -A INPUT -p tcp --dport 14121:14124 -j DROP3. Log Audit & IoC Verification Commands
Use the following PowerShell script to scan Output Messenger server logs for directory traversal patterns ('../', '..\', or URL-encoded equivalents) that indicate potential exploitation attempts.
# Scan Output Messenger logs for directory traversal indicators
$logPath = 'C:\Program Files\Output Messenger Server\Logs\*'
$patterns = @('\.\./', '\.\.\\', '%2e%2e%2f', '%2e%2e%5c')
foreach ($pattern in $patterns) {
Select-String -Path $logPath -Pattern $pattern -SimpleMatch | Select-Object Path, LineNumber, Line -First 20
}Block Exploits Instantly with Managed Virtual Patching Rules
Can't patch production immediately? Deploy managed WAF rules at the edge to intercept RCE, SQLi, and deserialization payloads before they hit your origin server.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2025-27920) is a directory traversal flaw in Output Messenger, an enterprise collaboration and messaging solution. The root cause lies in improper validation of file path parameters during file transfer or API requests. By failing to sanitize input parameters, the application allows attackers to inject directory traversal sequences ('../') to escape the designated root directory and access arbitrary paths on the host operating system.
2. Exploitation Mechanics & Attack Scenario
An authenticated attacker can craft malicious requests containing directory traversal sequences (e.g., 'filename=../../../../windows/win.ini' or 'config.json'). Because the server processes these inputs without proper sanitization, it resolves the path relative to the local file system, returning sensitive files to the attacker. This vulnerability has been actively exploited in the wild by threat actors (such as Marbled Dust) to exfiltrate configuration data and facilitate further compromise.
3. Infrastructure & Business Impact
Given its inclusion in the CISA KEV catalog, this vulnerability poses an immediate and severe threat to enterprise environments. Successful exploitation allows attackers to read sensitive configuration files, database credentials, and system files, which can be leveraged to achieve full remote code execution (RCE) and lateral movement. This compromises business continuity, leads to data exfiltration, and exposes internal networks to persistent threats.
Official Vendor Advisories & References
Output Messenger before 2.0.63 was vulnerable to a directory traversal attack through improper file path handling. By using ../ sequences in parameters, attackers could access sensitive files outside the intended directory, potentially leading to configuration leakage or arbitrary file access.
Frequently Asked SecOps Questions (CVE-2025-27920)
FAQQ1. How critical is CVE-2025-27920 and is it actively exploited in the wild?
CVE-2025-27920 is rated CVSS 8.8 (HIGH) with a 30-day EPSS exploitation probability of 1.9%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2025-27920?
Primary impacted vendors include srimax across output messenger. Scope summary: All Output Messenger versions prior to 2.0.63
Q3. What temporary mitigations or workarounds exist for CVE-2025-27920 before patching?
[Mitigation] Immediately upgrade Output Messenger to the latest secure version (2.0.63 or higher) and restrict network access Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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