CVE-2025-12240
Published: 27 October 2025
Summary
CVE-2025-12240 is a high-severity Improper Restriction of Operations within the Bounds of a Memory Buffer (CWE-119) vulnerability in Totolink A3300R Firmware. Its CVSS base score is 8.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 30.9% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-16 (Memory Protection).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Directly mitigates the buffer overflow by enforcing validation of the 'ip' argument in the setDmzCfg CGI function to prevent invalid input exploitation.
Addresses the specific buffer overflow flaw through timely identification, patching, and verification of firmware updates for the TOTOLINK A3300R router.
Implements memory protection mechanisms like stack canaries or ASLR to prevent successful exploitation of the buffer overflow even if input validation fails.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The buffer overflow in the router's public-facing web CGI endpoint (/cgi-bin/cstecgi.cgi setDmzCfg) enables remote code execution without authentication, directly mapping to exploitation of public-facing applications (T1190) and remote services (T1210).
NVD Description
A security vulnerability has been detected in TOTOLINK A3300R 17.0.0cu.557_B20221024. This affects the function setDmzCfg of the file /cgi-bin/cstecgi.cgi. The manipulation of the argument ip leads to buffer overflow. It is possible to initiate the attack remotely. The exploit has…
more
been disclosed publicly and may be used.
Deeper analysisAI
CVE-2025-12240 is a buffer overflow vulnerability (CWE-119, CWE-120) affecting the TOTOLINK A3300R router on firmware version 17.0.0cu.557_B20221024. The flaw exists in the setDmzCfg function of the /cgi-bin/cstecgi.cgi component, where manipulation of the "ip" argument triggers the overflow. Published on 2025-10-27, it carries a CVSS v3.1 base score of 8.8 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).
An attacker with low privileges, such as an authenticated user, can exploit this remotely over the network with low complexity and no user interaction required. Successful exploitation enables high-impact consequences, including unauthorized access to sensitive data, modification of system integrity, and denial of service through availability disruption.
Advisories note that a proof-of-concept exploit has been publicly disclosed on GitHub at https://github.com/noahze01/IoT-vulnerable/blob/main/TOTOLink/A3300R/setDmzCfg.md, and it may be used in attacks. Additional details are available via VulDB (https://vuldb.com/?ctiid.329910, https://vuldb.com/?id.329910, https://vuldb.com/?submit.673722), with the vendor site at https://www.totolink.net/ for potential patches or further guidance.
Details
- CWE(s)