CVE-2025-6752 in WRT1900ACS
Summary
by MITRE • 06/27/2025
A vulnerability has been found in Linksys WRT1900ACS, EA7200, EA7450 and EA7500 up to 20250619 and classified as critical. This vulnerability affects the function SetDefaultConnectionService of the file /upnp/control/Layer3Forwarding of the component IGD. The manipulation of the argument NewDefaultConnectionService leads to stack-based buffer overflow. The attack can be initiated remotely. The exploit has been disclosed to the public and may be used. The vendor was contacted early about this disclosure but did not respond in any way.
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Analysis
by VulDB Data Team • 06/27/2025
This critical vulnerability resides within the Internet Gateway Device implementation of several Linksys routers including the WRT1900ACS, EA7200, EA7450, and EA7500 models. The flaw manifests in the UPnP Layer3Forwarding control interface where the SetDefaultConnectionService function processes incoming requests. The vulnerability stems from improper input validation of the NewDefaultConnectionService parameter, which allows an attacker to supply malicious data exceeding the allocated buffer space. This specific implementation fails to perform adequate bounds checking before copying user-supplied data into a fixed-size stack buffer, creating a classic stack-based buffer overflow condition that can be exploited to execute arbitrary code on the affected devices.
The technical exploitation of this vulnerability occurs through remote network access to the UPnP control interface, which is typically exposed on port 1900 or other designated ports. Attackers can manipulate the NewDefaultConnectionService argument to overflow the stack buffer and potentially overwrite adjacent memory locations including return addresses, enabling code execution with the privileges of the UPnP service process. This type of vulnerability is classified as CWE-121 Stack-based Buffer Overflow, which represents a well-known and highly dangerous class of memory corruption vulnerabilities that have been extensively documented in the cybersecurity community. The attack vector is particularly concerning as it requires no authentication and can be executed from external networks, making these devices vulnerable to exploitation by remote threat actors without requiring physical access or prior credentials.
The operational impact of this vulnerability extends beyond simple code execution, as it can enable full device compromise and potential network infiltration. Successful exploitation could allow attackers to gain persistent access to the router's management interface, modify network configurations, redirect traffic, or establish backdoors for continued access. The vulnerability affects multiple generations of Linksys routers that are widely deployed in residential and small business environments, creating a substantial attack surface. The fact that this exploit has been publicly disclosed and is believed to be actively used increases the immediate risk to affected networks, particularly since the vendor did not provide any response to early disclosure attempts, indicating potential lack of available patches or firmware updates for these specific models.
Organizations and individuals should immediately implement network segmentation to isolate affected devices from critical network infrastructure, disable UPnP services where possible, and monitor network traffic for suspicious activity related to UPnP communications. The recommended mitigation strategies include applying firmware updates from Linksys as soon as they become available, implementing network access controls to restrict UPnP traffic, and conducting thorough network assessments to identify all affected devices. Security professionals should also consider implementing intrusion detection systems with signatures specifically targeting UPnP buffer overflow exploitation attempts, as this vulnerability aligns with ATT&CK technique T1071.004 Application Layer Protocol: DNS, where attackers may use compromised devices to establish command and control communications. The vulnerability demonstrates the importance of proper input validation and memory safety practices in embedded network devices, as outlined in industry security frameworks such as the NIST Cybersecurity Framework and ISO/IEC 27001 standards for information security management.