CVE Alert: CVE-2025-9527 – Linksys – E1700

Risk verdict

High risk: remote, low-privilege exploitation is possible with a public PoC, so patching should be prioritised.

Why this matters

The issue enables stack-based memory corruption with full impact on confidentiality, integrity and availability. With consumer routers like the Linksys E1700 being widely deployed in homes and small networks, an attacker could disrupt services, seize control of the device, or pivot to connected hosts.

Most likely attack path

An attacker would reach the QoSSetup endpoint (/goform/QoSSetup) over the network, send crafted data to the ack_policy argument, and trigger a stack overflow. No user interaction is required, and only low privileges are needed, increasing the likelihood of automated attempts. If exploitation succeeds, the attacker could crash or take control of the device, enabling further lateral movement within the local network.

Who is most exposed

Common in residential and small-office deployments, often exposed to the WAN or inadequately restricted management interfaces. Enterprises with legacy home-network gear or misconfigured remote management are particularly at risk.

Detection ideas

• Unexpected router reboots or memory crash logs tied to QoSSetup.
• Anomalous or oversized requests to /goform/QoSSetup, especially with crafted ack_policy values.
• Elevated CPU or memory usage correlating with remote management traffic.
• Indicators of attempted exploitation in network firewall/IDS logs targeting the QoS endpoint.

Mitigation and prioritisation

• Apply vendor patch or upgrade to the fixed version; verify remediation in staging before production.
• If patching is not possible, disable or tightly restrict remote management and QoSSetup access (block WAN access, enforce ACLs).
• Enable strong network segmentation and monitor for PoC indicators or anomal QoS traffic.
• Review change-management and schedule downtime for firmware update.
• If KEV true or EPSS ≥ 0.5, treat as priority 1.