A critical zero-day remote code execution (RCE) vulnerability, identified as CVE-2025-9961, has been discovered in TP-Link routers.
Security research firm ByteRay has released a proof-of-concept (PoC) exploit, demonstrating how attackers can bypass Address Space Layout Randomization (ASLR) protections to gain full control over affected devices.
The vulnerability resides in the router’s Customer Premises Equipment (CPE) WAN Management Protocol (CWMP) binary, a component of the TR-069 protocol used by service providers for remote device management.
Technical Breakdown of the Exploit
The core of the vulnerability is a stack-based buffer overflow within the cwmp process. Researchers at ByteRay found that by sending a malicious request, they could overwrite the program counter (PC) and seize control of the execution flow.
However, the presence of ASLR, a security feature that randomizes the memory addresses of key data areas, presented a significant hurdle.
Since the exploit did not involve an information leak to disclose memory layouts, the researchers devised a brute-force strategy. They repeatedly guessed the base address of the standard C library (libc) to locate the system() function.
An incorrect guess would crash the cwmp service, but the researchers noted that an attacker with access to the TP-Link web panel could simply restart the service, making the brute-force attack practical.
The attack workflow requires the router to be configured to accept the attacker’s custom Auto Configuration Server (ACS). The exploit is delivered through a SetParameterValues request containing the payload.
The final payload uses a return-to-libc (ret2libc) technique to call the system() function with a command argument.
This command instructs the router to download and execute a malicious binary (e.g., a reverse shell) from an attacker-controlled server, granting the attacker complete remote access.
Discovery and PoC Release
The ByteRay research team made the discovery. During their analysis, they encountered a problem where the standard GenieACS platform corrupted the binary payload, preventing successful exploitation. This forced them to develop a custom ACS emulator capable of faithfully transmitting the exploit code.
The team has published a detailed technical write-up and the full exploit code on GitHub. They state the release is intended for educational purposes and security research, allowing administrators to test their own devices. Unauthorized use of other systems is illegal.
This vulnerability is critical, as successful exploitation allows for complete remote code execution on the router. This could enable an attacker to intercept traffic, launch further attacks on the local network, or enlist the device in a botnet.
The research underscores the security risks associated with network-facing management protocols like TR-069, where even minor parsing errors can escalate into severe threats.
The exploit highlights that security mitigations like ASLR can sometimes be bypassed with creative attack strategies.
Users of TP-Link routers are advised to monitor for firmware updates from the vendor and apply them as soon as they become available to patch this vulnerability.
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