Three design and multiple implementation flaws have been disclosed in IEEE 802.11 technical standard that undergirds Wi-Fi, potentially enabling an adversary to take control over a system and plunder confidential data.

Called FragAttacks (short for FRgmentation and AGgregation Attacks), the weaknesses impact all Wi-Fi security protocols, from Wired Equivalent Privacy (WEP) all the way to Wi-Fi Protected Access 3 (WPA3), thus virtually putting almost every wireless-enabled device at risk of attack.

"An adversary that is within radio range of a victim can abuse these vulnerabilities to steal user information or attack devices," Mathy Vanhoef, a security academic at New York University Abu Dhabi, said. "Experiments indicate that every Wi-Fi product is affected by at least one vulnerability and that most products are affected by several vulnerabilities."

IEEE 802.11 provides the basis for all modern devices using the Wi-Fi family of network protocols, allowing laptops, tablets, printers, smartphones, smart speakers, and other devices to communicate with each other and access the Internet via a wireless router.

Introduced in January 2018, WPA3 is a third-generation security protocol that's at the heart of most Wi-Fi devices with several enhancements such as robust authentication and increased cryptographic strength to safeguard wireless computer networks.

According to Vanhoef, the issues stem from "widespread" programming mistakes encoded in the implementation of the standard, with some flaws dating all the way back to 1997. The vulnerabilities have to do with the way the standard fragments and aggregates frames, allowing threat actors to inject arbitrary packets and trick a victim into using a malicious DNS server, or forge the frames to siphon data.

The list of 12 flaws is as follows —

  • CVE-2020-24588: Accepting non-SPP A-MSDU frames
  • CVE-2020-24587: Reassembling fragments encrypted under different keys
  • CVE-2020-24586: Not clearing fragments from memory when (re)connecting to a network
  • CVE-2020-26145: Accepting plaintext broadcast fragments as full frames (in an encrypted network)
  • CVE-2020-26144: Accepting plaintext A-MSDU frames that start with an RFC1042 header with EtherType EAPOL (in an encrypted network)
  • CVE-2020-26140: Accepting plaintext data frames in a protected network
  • CVE-2020-26143: Accepting fragmented plaintext data frames in a protected network
  • CVE-2020-26139: Forwarding EAPOL frames even though the sender is not yet authenticated
  • CVE-2020-26146: Reassembling encrypted fragments with non-consecutive packet numbers
  • CVE-2020-26147: Reassembling mixed encrypted/plaintext fragments
  • CVE-2020-26142: Processing fragmented frames as full frames
  • CVE-2020-26141: Not verifying the TKIP MIC of fragmented frames

A bad actor can leverage these flaws to inject arbitrary network packets, intercept and exfiltrate user data, launch denial-of-service attacks, and even possibly decrypt packets in WPA or WPA2 networks.

"If network packets can be injected towards a client, this can be abused to trick the client into using a malicious DNS server," Vanhoef explained in an accompanying research paper. "If network packets can be injected towards an [access point], the adversary can abuse this to bypass the NAT/firewall and directly connect to any device in the local network."

In a hypothetical attack scenario, these vulnerabilities can be exploited as a stepping stone to launch advanced attacks, permitting an attacker to take over an outdated Windows 7 machine inside a local network. But on a brighter note, the design flaws are hard to exploit as they require user interaction or are only possible when using uncommon network settings.

The findings have been shared with the Wi-Fi Alliance, following which firmware updates were prepared during a 9-month-long coordinated disclosure period. Microsoft, for its part, released fixes for some of the flaws (CVE-2020-24587, CVE-2020-24588, and CVE-2020-26144) as part of its Patch Tuesday update for May 2021. Vanhoef said an updated Linux kernel is in the works for actively supported distributions.

This is not the first time Vanhoef has demonstrated severe flaws in the Wi-Fi standard. In 2017, the researcher disclosed what's called KRACKs (Key Reinstallation AttACKs) in WPA2 protocol, enabling an attacker to read sensitive information and steal credit card numbers, passwords, messages, and other data.

"Interestingly, our aggregation attack could have been avoided if devices had implemented optional security improvements earlier," Vanhoef concluded. "This highlights the importance of deploying security improvements before practical attacks are known. The two fragmentation based design flaws were, at a high level, caused by not adequately separating different security contexts. From this we learn that properly separating security contexts is an important principle to take into account when designing protocols."

Mitigations for FragAttacks from other companies like Cisco, HPE/Aruba Networks, Juniper Networks, and Sierra Wireless can be accessed in the advisory released by the Industry Consortium for Advancement of Security on the Internet (ICASI).

"There is no evidence of the vulnerabilities being used against Wi-Fi users maliciously, and these issues are mitigated through routine device updates that enable detection of suspect transmissions or improve adherence to recommended security implementation practices," the Wi-Fi Alliance said.


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