CVE-2026-4566
Published: 23 March 2026
Summary
CVE-2026-4566 is a high-severity Improper Restriction of Operations within the Bounds of a Memory Buffer (CWE-119) vulnerability. Its CVSS base score is 7.4 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 47.9th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-16 (Memory Protection).
Deeper analysis
CVE-2026-4566 is a stack-based buffer overflow vulnerability in the Belkin F9K1122 router running firmware version 1.00.33. The flaw resides in the formWISP5G function within the /goform/formWISP5G file, where manipulation of the "webpage" argument triggers the overflow. This issue is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) and CWE-121 (Stack-based Buffer Overflow), with a CVSS v3.1 base score of 8.8.
The vulnerability can be exploited remotely by an attacker with low privileges over the network, requiring low attack complexity and no user interaction. Successful exploitation grants high impacts on confidentiality, integrity, and availability, potentially allowing arbitrary code execution on the affected device.
Advisories from VulDB and referenced GitHub repositories, including a proof-of-concept exploit, confirm the issue but note that the vendor was contacted early without any response or patch release. No mitigations or firmware updates are available from Belkin at this time.
A proof-of-concept exploit has been publicly disclosed on GitHub, increasing the risk of widespread abuse against unpatched Belkin F9K1122 devices.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-14347
Vulnerability details
A flaw has been found in Belkin F9K1122 1.00.33. The affected element is the function formWISP5G of the file /goform/formWISP5G. Executing a manipulation of the argument webpage can lead to stack-based buffer overflow. The attack can be launched remotely. The…
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exploit has been published and may be used. The vendor was contacted early about this disclosure but did not respond in any way.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The CVE describes a remotely exploitable stack-based buffer overflow in the web interface of a public-facing Belkin router, enabling arbitrary code execution with low complexity and no user interaction, directly mapping to T1190: Exploit Public-Facing Application.
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Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Requires validation of the 'webpage' argument in the formWISP5G function to directly prevent the stack-based buffer overflow exploitation.
Implements memory protections such as stack canaries and non-executable stacks to block arbitrary code execution from the buffer overflow.
Mandates identification, reporting, and remediation of the specific flaw in Belkin F9K1122 firmware version 1.00.33, including patching or device replacement.