Known exploited · Realtek
CVE-2021-35395: Realtek AP-Router SDK Buffer Overflow Vulnerability
What it is
Realtek AP-Router SDK HTTP web server boa contains a buffer overflow vulnerability due to unsafe copies of some overly long parameters submitted in the form that lead to denial-of-service (DoS).
- Vendor
- Realtek
- Product
- AP-Router SDK
- Added to KEV
- November 3, 2021
- CISA due date
- November 17, 2021
- Ransomware use
- Unknown
What CISA requires
Apply updates per vendor instructions.
Forensic triage
No
What to do now
- Find every instance of AP-Router SDK you run, including the forgotten ones, and check its version against the vendor advisory.
- Apply the vendor's fix or mitigation, before November 17, 2021 if you are bound by CISA's deadline, sooner if it faces the internet.
- Assume it was tried against you already: look for signs of exploitation from the date it was added, not from the day you patched.
References
H2 Security
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Start freeSource: CISA Known Exploited Vulnerabilities Catalog (public domain), catalog version 2026.10.01.