CVE-2025-8939
Published: 14 August 2025
Summary
CVE-2025-8939 is a high-severity Improper Restriction of Operations within the Bounds of a Memory Buffer (CWE-119) vulnerability in Tenda Ac20 Firmware. Its CVSS base score is 7.4 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 18.2% 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).
Deeper analysis
A vulnerability identified as CVE-2025-8939 affects Tenda AC20 routers running firmware up to version 16.03.08.12. It resides in an unspecified function within the /goform/WifiGuestSet endpoint, where improper handling of the shareSpeed argument triggers a buffer overflow. The issue is tracked under CWE-119 and CWE-120 and carries a CVSS 4.0 score of 7.4, reflecting network-accessible attack conditions with low complexity and high impact on confidentiality, integrity, and availability.
An authenticated remote attacker can supply a crafted shareSpeed value to the affected endpoint, causing memory corruption that may lead to arbitrary code execution or denial of service. Public proof-of-concept code has been released, confirming that exploitation is feasible over the network without user interaction once valid credentials are obtained.
The EPSS score remains flat at 0.0155 with no material increase since disclosure. Available references consist of public disclosure and proof-of-concept repositories rather than vendor advisories describing patches or configuration mitigations.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-24671
Vulnerability details
A vulnerability was determined in Tenda AC20 up to 16.03.08.12. Affected is an unknown function of the file /goform/WifiGuestSet. The manipulation of the argument shareSpeed leads to buffer overflow. It is possible to launch the attack remotely. The exploit has…
more
been disclosed to the public and may be used.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Buffer overflow in the public-facing web interface (/goform/WifiGuestSet) of Tenda AC20 router enables remote exploitation for potential code execution.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Requires validation of the shareSpeed argument in the /goform/WifiGuestSet endpoint to prevent buffer overflow from improper input handling.
Implements memory protections such as stack canaries, ASLR, and DEP to mitigate exploitation of the buffer overflow vulnerability leading to remote code execution.
Mandates timely remediation of the buffer overflow flaw in Tenda AC20 firmware up to version 16.03.08.12 to eliminate the vulnerability.