CVE-2026-5042
Published: 29 March 2026
Summary
CVE-2026-5042 is a high-severity Improper Restriction of Operations within the Bounds of a Memory Buffer (CWE-119) vulnerability in Belkin F9K1122 Firmware. 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 47.3th percentile by exploit likelihood (below the median); 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
CVE-2026-5042 is a stack-based buffer overflow vulnerability affecting the Belkin F9K1122 router on firmware version 1.00.33. The issue lies in the formCrossBandSwitch function within the /goform/formCrossBandSwitch file of the Parameter Handler component, triggered by manipulation of the "webpage" argument. Associated CWEs include CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), CWE-121 (Stack-based Buffer Overflow), and CWE-787 (Out-of-bounds Write). The vulnerability was published on 2026-03-29 and 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 can exploit this remotely over the network with low complexity and no user interaction required. Successful exploitation grants high impacts on confidentiality, integrity, and availability, potentially allowing arbitrary code execution or system compromise. A public exploit has been released, increasing the risk of real-world attacks.
Advisories from VulDB and a related GitHub repository document the issue but note that the vendor was contacted early without any response. No patches or official mitigations are available based on the disclosure. Practitioners should review the references—such as https://github.com/Litengzheng/vul_db/blob/main/Belkin/vul_153/README.md and https://vuldb.com/vuln/353965—for exploit details and monitor for updates.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-16987
Vulnerability details
A security flaw has been discovered in Belkin F9K1122 1.00.33. The affected element is the function formCrossBandSwitch of the file /goform/formCrossBandSwitch of the component Parameter Handler. The manipulation of the argument webpage results in stack-based buffer overflow. The attack may…
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be launched remotely. The exploit has been released to the public and may be used for attacks. 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 vulnerability is a stack-based buffer overflow in the web management interface (formCrossBandSwitch) of a public-facing router, enabling remote exploitation for arbitrary code execution, directly mapping to Exploit Public-Facing Application.
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Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Requires timely remediation of known flaws like the stack-based buffer overflow in CVE-2026-5042 through patching or approved mitigations.
Implements memory protection mechanisms such as stack canaries, ASLR, and DEP to mitigate stack-based buffer overflows exploited via the 'webpage' argument.
Enforces validation of information inputs like the 'webpage' argument to prevent improper restriction of operations leading to buffer overflows.