Critical Broadcom Chipset Vulnerability Disrupts Networks on ASUS Routers
Published
Key Takeaways
- Critical Flaw: A high-severity flaw in Broadcom chipsets allows attackers to terminate client connections on 5 GHz networks via a single over-the-air frame.
- Hardware Impact: It impacts the ASUS RT-BE86U wireless router, though other devices utilizing the same software may also be susceptible to similar denial-of-service attacks.
- Remediation: Broadcom has issued a software patch to its partners, and ASUS has released firmware updates to resolve the issue.
A significant vulnerability affecting Broadcom chipset software was uncovered during interoperability testing of the Defensics Fuzzing 802.11 protocol test suites against ASUS routers. Researchers observed that specific anomaly test cases caused the router's 5 GHz network to become unresponsive, effectively disconnecting all clients and halting data transmission.
The disruption persists until the device is manually reset, creating a persistent denial-of-service (DoS) condition.
Technical Exploitation and Network Impact
This Broadcom chipset vulnerability, with a CVSS 4.0 score of 8.4 (High), allows an unauthenticated attacker within range to cripple a target network by transmitting a single specific frame over the air, the Black Duck Cybersecurity Research Center (CyRC) said in an advisory released today.
The attack vector functions independently of the configured network security level, making it highly effective against both secured and open networks. Upon exploitation, the 5 GHz band, including guest networks, ceases to function, although Ethernet connections and the 2.4 GHz band remain operational.
The vulnerability impacts versions 3.0.0.6.102_37812 and older, and specifically allows an attacker to:
- Disable a router’s 5 GHz network with a single malformed frame
- Immediately disconnect all active clients and block reconnection
- Bypass WPA2 and WPA3 protections
- Repeat the attack indefinitely until the router is manually restarted
While specific technical details have been withheld to prevent widespread malicious use, the ease of exploitation poses a substantial risk to network infrastructure stability.
Mitigation and Firmware Updates
Following the discovery, the ASUS Product Security Incident Response Team (PSIRT) collaborated with Broadcom to trace the root cause to the chipset software. Broadcom has since released a patched version of the software to its customers.
To mitigate the ASUS router network disruption, users are strongly advised to update their firmware immediately. For the tested ASUS RT-BE86U model, firmware versions 3.0.0.6.102_37841 and later contain the necessary fix. Device manufacturers utilizing affected Broadcom software are responsible for integrating the patch into their respective firmware releases.
A report earlier this month flagged a critical RCE flaw in legacy D-Link DSL router models that ultimately requires device replacement.
Recommendations from Cybersecurity Experts
James Maude, Field CTO at BeyondTrust, stated that risks potentially include opening the door to “evil twin attacks where the real access point is knocked offline, and a rogue one with the same name and password replaces it.”
Implementation-level flaws in protocols, such as 802.11, are often more difficult to detect than cryptographic weaknesses, said Ben Ronallo, Principal Cybersecurity Engineer at Black Duck, who recommends auditing and replacing end-of-life/support systems – otherwise, lock them down, have redundant logging in place, and monitor network edges with intrusion detection/prevention.
“If you’re building networking in a hospital or your own home, segment your networks to prevent a direct path to your critical systems,” he added.
Saumitra Das, Vice President of Engineering at Qualys, said that security teams can prioritize patching in an organized and risk-driven way by tagging assets with business context.
Randolph Barr, CISO at Cequence Security, recommends that organizations prioritize firmware updates from vendors and confirm their implementation; consider wireless connectivity failures as possible signs of security problems; and ensure there is an outage action plan that employees follow.
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