Researchers from UC Riverside developed attacks able to bypass client isolation in Wi-Fi networks used at home, at work, in airports, and in coffee shops.
Four computer scientists from Riverside, and one from KU Leuven (Belgium) found that every router and network they tested was vulnerable to at least one attack. Their findings are detailed in a paper (AirSnitch: Demystifying and Breaking Client Isolation in Wi-Fi Networks) presented at the NDSS Symposium 2026.
Wi-Fi client isolation, also known as Access Point (AP) isolation or station isolation, is the security feature that ensures Wi-Fi clients cannot intercept, transmit, or inject traffic from or to other clients within the same wireless local area network.
If client isolation is active, the primary role of the AP device in switching traffic from source to destination is no longer allowed. This prevents any direct connection between multiple devices on the network – the only destination allowed is upstream to a router. This rule allows most (not all) legitimate work to continue, but prevents malware spreading between devices, snooping on public Wi‑Fi, and blocks port scanning and ARP spoofing.
The problem, according to the researchers, is that isolation can be bypassed. “We believe that a root cause of these vulnerabilities is the missing standardization of client isolation,” write the researchers: “This defense was added by vendors without proper public review.” The lack of standardization, they say, leads to inconsistent, ad hoc, and often incomplete implementations of isolation across vendors.
They found three primary weaknesses in client isolation implementations that allowed them to develop their attacks.
Firstly, the abusing GTK attack. The Wi-Fi keys that protect broadcast frames are improperly managed and can be abused to bypass client isolation. Most Wi-Fi implementations used a shared group temporal key to protect broadcast or multicast communications; and all clients frequently have access to this key during client isolation. “This key can be abused by an insider to directly inject packets to victims, bypassing client isolation at the AP,” say the researchers.
Secondly, the gateway bouncing attack. isolation is often only enforced at the MAC or IP layer, but not both. “We find that an attacker can inject packets to a victim, by using the AP’s gateway MAC address as the layer 2 destination, but the victim’s IP address as the layer 3 destination,” say the researchers.
“These packets are typically accepted by the AP and forwarded to the gateway. If the gateway does not enforce client isolation at the IP layer, it will forward the datagram to its destination i.e., the victim client on the Wi-Fi network, allowing the attacker to reach the ‘layer-2 isolated’ victim clients.”
Thirdly, a Machine-in-the-Middle (MitM )attack. Weak synchronization of a client’s identity across the network stack allows one to bypass Wi-Fi client isolation at the network layer instead, enabling the interception of uplink and downlink traffic of other clients as well as internal backend devices.
Spoofing the victim’s MAC address allows an attacker to intercept downlink frames. Obtaining uplink traffic is obtainable by impersonating internal backend devices such as the gateway by spoofing the MAC address. “Surprisingly, even though this results in client-to-client traffic, it is often allowed by the network. Combined with our other techniques, this results in a full bi-directional MitM,” say the researchers.
Not all Wi-Fi networks are susceptible to all three attacks, but the researchers did not find any network that could not be exploited by at least one method. The results of the research were responsibly provided to manufacturers who were given more than 90 days to develop fixes before the paper was published. But the researchers warn that full solutions for all Wi-Fi networks will be difficult.
They say, “Because our attacks exploit multiple protocols, standards, and their cross-layer interactions, it is difficult for a single vendor to recognize the full security impact in isolation. As a result, effective long-term mitigation requires ecosystem-level coordination across standards bodies, device manufacturers, and network operators.”
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