CVE-2025-29846: Synology Router Manager Disclosure Flaw

CVE-2025-29846 Overview

CVE-2025-29846 is a path traversal vulnerability [CWE-22] in the portenable CGI component of Synology Router Manager (SRM). The flaw allows remote authenticated users with high privileges to retrieve the status of installed packages on the affected router. Synology disclosed the issue in security advisory Synology_SA_25_04, confirming impact on SRM version 1.3.1-9346 and its update releases.

The vulnerability affects the confidentiality, integrity, and availability of the router platform despite requiring authenticated access. Exploitation is network-reachable and requires no user interaction.

Critical Impact
Authenticated attackers can query the status of installed packages through the portenable CGI interface, exposing configuration data useful for follow-on attacks against the router.

Affected Products

Synology Router Manager 1.3.1-9346 (base release)
Synology Router Manager 1.3.1-9346 updates 1 through 12
Synology routers running vulnerable SRM firmware versions

Discovery Timeline

2025-12-04 - CVE-2025-29846 published to NVD
2025-12-05 - Last updated in NVD database

Technical Details for CVE-2025-29846

Vulnerability Analysis

The portenable CGI handler in Synology Router Manager processes requests related to port and package state management. The component fails to enforce restrictions on the resources it inspects, allowing authenticated users to traverse paths and read installed package status data they should not access.

The flaw is categorized as [CWE-22] Improper Limitation of a Pathname to a Restricted Directory, more commonly referred to as path traversal. Although the description emphasizes information retrieval, the advisory reflects impact across confidentiality, integrity, and availability. Attackers reaching the CGI endpoint over the network can enumerate package state and leverage that data to plan privileged operations.

The EPSS probability for this CVE is 0.834% with a percentile of 74.937, indicating moderate predicted exploitation interest compared to the broader CVE population.

Root Cause

The root cause is insufficient input validation and path canonicalization within the portenable CGI binary. The handler accepts user-controlled parameters that influence which package or resource state is queried without restricting traversal sequences or validating the resolved path against an allowlist.

Attack Vector

Exploitation requires an authenticated session with high privileges on the router web interface. Once authenticated, the attacker issues a crafted HTTP request to the portenable CGI endpoint with parameters that traverse outside the intended directory or reference packages the user should not inspect. The server responds with package status information, enabling reconnaissance of installed software, version states, and potential downstream targets.

No public proof-of-concept exploit has been published, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. Refer to the Synology Security Advisory SA-25-04 for vendor-provided technical context.

Detection Methods for CVE-2025-29846

Indicators of Compromise

HTTP requests to the SRM portenable CGI endpoint containing traversal sequences such as ../ or encoded variants like %2e%2e%2f
Authenticated administrative sessions issuing repeated package-status queries from unfamiliar source IP addresses
Web access logs showing enumeration patterns against /webapi/ or CGI paths handling package state

Detection Strategies

Inspect SRM web server access logs for anomalous parameter values targeting portenable and related CGI handlers
Correlate administrative authentication events with subsequent package-state queries to identify reconnaissance behavior
Alert on path traversal signatures in HTTP request URIs and query strings reaching the router management interface

Monitoring Recommendations

Forward SRM system and access logs to a centralized SIEM for retention and correlation
Monitor for new or unexpected administrative account logins, particularly from external networks
Track firmware version inventory to confirm all routers have been updated past the vulnerable 1.3.1-9346 update branch

How to Mitigate CVE-2025-29846

Immediate Actions Required

Apply the SRM firmware update referenced in Synology Security Advisory SA-25-04 to all affected routers
Restrict administrative access to the router management interface to trusted internal networks only
Rotate administrator credentials and audit all accounts with high privileges on affected devices

Patch Information

Synology has published guidance and fixed firmware through advisory Synology_SA_25_04. Administrators should upgrade Synology Router Manager beyond the vulnerable 1.3.1-9346 update releases as specified in the vendor advisory. Confirm the running firmware version through the SRM control panel after applying the update.

Workarounds

Disable remote administrative access via WAN and require VPN connectivity for management traffic
Enforce strong, unique administrator passwords and enable two-factor authentication on SRM accounts
Limit the number of accounts granted administrator-level privileges to reduce the authenticated attack surface

bash

# Example: restrict SRM admin interface to a management subnet using firewall rules
# Adjust the management network and WAN interface to match your environment
iptables -A INPUT -i eth0 -p tcp --dport 8001 -s 10.10.0.0/24 -j ACCEPT
iptables -A INPUT -i eth0 -p tcp --dport 8001 -j DROP