Buffer Overflow in Realtek AP‑Router SDK (CVE‑2021‑35395) Enables Denial‑of‑Service
What It Is – Realtek’s AP‑Router SDK HTTP web server contains an unsafe copy operation that can be triggered by an overly‑long parameter, resulting in a stack‑based buffer overflow. The flaw can be leveraged to crash the web server, causing a denial‑of‑service condition.
Exploitability – The vulnerability is publicly disclosed (CVE‑2021‑35395) and a proof‑of‑concept exists. No remote code execution is reported, but an attacker can reliably cause service disruption without authentication.
Affected Products – Realtek AP‑Router SDK (all versions shipping the vulnerable HTTP server component).
Why It Matters for Trust & Control Assurance
- Vulnerability Management – Demonstrates the need for a documented process to discover, assess, and remediate software flaws in network‑infrastructure components.
- Continuous Evidence – Timely patching and verification provide audit‑ready evidence that the organization is actively managing risk, a key control objective across frameworks (e.g., NIST CSF Identify & Protect).
- Defensible Incident Response – Knowing the exact vector (buffer overflow) enables precise logging and detection rules, supporting a credible incident‑response posture that buyers increasingly demand.
Recommended Actions
- Inventory all devices running Realtek AP‑Router SDK and verify version levels.
- Apply Realtek‑issued patches or upgrade to a non‑vulnerable SDK release.
- Integrate the CVE into your vulnerability‑scanning schedule and ensure remediation is tracked in your ticketing system.
- Enable detailed web‑server logging and monitor for abnormal request lengths or crashes.
- Map the remediation steps to your vulnerability‑management control objective to generate audit evidence.
Source: CISA KEV – CVE‑2021‑35395