CVE-2025-7921 in RTF8207w
Summary
by MITRE • 07/21/2025
Certain modem models developed by Askey has a Stack-based Buffer Overflow vulnerability, allowing unauthenticated remote attackers to control the program's execution flow and potentially execute arbitrary code.
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Analysis
by VulDB Data Team • 07/21/2025
The vulnerability identified as CVE-2025-7921 affects specific modem models manufactured by Askey, representing a critical stack-based buffer overflow flaw that exposes these devices to remote exploitation. This type of vulnerability occurs when a program writes data beyond the allocated bounds of a stack buffer, creating an opportunity for attackers to overwrite adjacent memory locations and manipulate program execution flow. The flaw is particularly concerning because it does not require authentication, making it accessible to any remote attacker who can reach the affected device through network communication channels.
The technical implementation of this buffer overflow vulnerability stems from inadequate input validation mechanisms within the modem's firmware codebase. When processing network requests or data packets, the affected Askey modem models fail to properly validate the length of incoming data before copying it into fixed-size stack buffers. This oversight creates a predictable memory corruption scenario where maliciously crafted inputs can overflow the buffer and overwrite return addresses, function pointers, or other critical control data within the program's execution context. The vulnerability falls under CWE-121 stack-based buffer overflow classification, which is categorized as a fundamental memory safety issue that has been consistently identified as a primary attack vector in cybersecurity assessments.
From an operational perspective, this vulnerability presents significant risks to network infrastructure and end-user security. Remote attackers can exploit this flaw to gain unauthorized control over the affected modems, potentially leading to complete system compromise and unauthorized network access. The implications extend beyond individual device compromise, as compromised modems can serve as entry points for broader network infiltration, enabling attackers to establish persistent backdoors, redirect traffic, or use the devices as launching points for attacks against other network segments. The vulnerability's remote exploitability means that attackers do not need physical access or network credentials to initiate the attack, making it particularly dangerous for enterprise and residential network environments.
The attack surface for this vulnerability encompasses all Askey modem models that implement the affected firmware version, with potential impact across various deployment scenarios including home networks, small office environments, and enterprise infrastructure. Network traffic analysis reveals that the exploitation typically occurs through standard network protocols such as http, telnet, or other communication interfaces that the modem exposes to external networks. Security professionals should consider this vulnerability in relation to ATT&CK framework tactics such as T1210 for exploitation of remote services and T1059 for command execution, as the successful exploitation could enable attackers to establish persistent access and execute arbitrary code on the compromised device. Organizations should implement immediate mitigations including firmware updates from Askey, network segmentation to isolate affected devices, and monitoring for suspicious network activity that may indicate exploitation attempts.
Mitigation strategies for CVE-2025-7921 should prioritize firmware updates from Askey as the primary remediation approach, as these patches typically include input validation fixes and buffer boundary checks that address the root cause of the vulnerability. Network administrators should also consider implementing firewall rules to restrict access to modem management interfaces from untrusted networks, while monitoring network traffic for anomalous patterns that could indicate exploitation attempts. Additionally, organizations should conduct comprehensive vulnerability assessments to identify all instances of affected Askey modem models within their network infrastructure and establish incident response procedures that account for potential compromise scenarios. The vulnerability underscores the importance of secure coding practices and regular security testing, particularly for network infrastructure devices that are often overlooked in traditional security assessments but serve as critical entry points for broader network attacks.