CVE-2026-13580: Buffer Overflow in Edimax EW-7478APC Firmware 1.04

Technical summary

CVE-2026-13580 is a classic stack-based or heap-based buffer overflow (CWE-119, CWE-120) in the formQoS function of the Edimax EW-7478APC firmware 1.04. The vulnerable code path processes the selSSID parameter from POST requests to /goform/formQoS without proper bounds checking, enabling an unauthenticated or authenticated attacker to write beyond allocated memory. This can lead to denial of service via crash or potential code execution depending on memory layout, ASLR availability, and the device's architecture (likely ARM-based). The vulnerability requires valid authentication (PR:L in CVSS vector), making it a post-authentication remote code execution risk.

Business impact

Organizations deploying Edimax EW-7478APC devices face operational disruption if exploited for denial of service, requiring out-of-band device recovery. More critically, successful code execution could allow an attacker with internal network access or compromised credentials to establish persistence, pivot to other network segments, or intercept wireless traffic. This is particularly concerning in managed service environments, education networks, and SMB deployments where these devices are common and credential compromise may occur through phishing or lateral movement.

Affected systems

Edimax EW-7478APC firmware version 1.04 is confirmed affected. Organizations should check whether they have deployed this device model and verify the firmware version via the device's web interface (typically accessible at 192.168.0.1). Determine if firmware updates addressing this issue have been released by checking Edimax's support portal. Note: vendor contact attempts appear to have gone unanswered, so patch availability should be verified independently.

Exploitability

The vulnerability is exploitable remotely but requires valid authentication credentials, which moderates immediate risk in perimeter-facing scenarios. However, the public disclosure of this vulnerability increases the probability of exploitation tools being developed or shared. The attack vector requires knowledge of valid credentials and network access to the device's web interface—either through direct access if the device is Internet-facing or through compromised internal accounts. Attackers already present on the internal network with user credentials represent the most credible threat.

Remediation

Immediate actions: (1) Check all Edimax EW-7478APC devices for firmware version 1.04 and document inventory. (2) Contact Edimax support directly to confirm whether a patched firmware version exists for this model. (3) If no patch is available, implement network segmentation to restrict administrative access to the device's web interface (port 80/443) to trusted management subnets only. (4) Enforce strong authentication on the device if not already configured (change default credentials). (5) Monitor for suspicious POST requests to /goform/formQoS with large selSSID payloads. Consider replacing the affected device with an alternative if no patch is forthcoming within a defined timeframe.

Patch guidance

Verify Edimax's official product support page for EW-7478APC to determine whether a firmware update addressing this issue is available. If a patched version exists, download it only from Edimax's official website, verify the checksum, and apply it during a maintenance window. If no patch is available, escalate to Edimax support using the public disclosure as reference (CVE-2026-13580, published 2026-06-29) and request an ETA. Document the date of contact and response for compliance records.

Detection guidance

Monitor network traffic and device logs for: (1) Repeated POST requests to /goform/formQoS from unexpected source IPs; (2) POST requests with unusually large payloads in the selSSID parameter (exceeding typical SSID length of 32 characters); (3) device reboots or crashes coinciding with suspicious web traffic; (4) failed or successful authentication attempts followed by the above patterns. Enable verbose logging on the access point if available. For network-based detection, deploy IDS/IPS rules targeting oversized QoS configuration requests or known exploit signatures (check security vendor feeds for any available detection content).

Why prioritize this

This vulnerability scores CVSS 8.8 (HIGH severity) due to high confidentiality, integrity, and availability impact combined with low attack complexity. Although it requires authentication, the presence of public exploit disclosure and the vendor's lack of response elevate the practical risk. Prioritize patching or mitigation for any EW-7478APC instances serving critical network functions or deployed in environments where credential compromise is plausible (post-breach scenarios, high-turnover organizations).

Risk score, explained

The CVSS 3.1 score of 8.8 reflects: Network attack surface (AV:N), low complexity (AC:L), requirement for valid credentials (PR:L), no user interaction needed (UI:N), and complete impact across confidentiality (C:H), integrity (I:H), and availability (A:H). The score does not account for mitigating factors such as network segmentation or strong credential hygiene—organizations implementing such controls should assess their residual risk accordingly. The public disclosure of the vulnerability and vendor non-responsiveness are not captured in CVSS but materially increase exploitation probability.

Frequently asked questions