CVE-2020-24588: IEEE 802.11 Wi-Fi Standard RCE Vulnerability

CVE-2020-24588 Overview

CVE-2020-24588 is a design vulnerability in the IEEE 802.11 standard that underpins Wi-Fi Protected Access (WPA, WPA2, and WPA3) and Wired Equivalent Privacy (WEP). The vulnerability exists because the standard does not require that the A-MSDU (Aggregate MAC Service Data Unit) flag in the plaintext QoS header field is authenticated. This fundamental weakness allows an adversary within wireless range to abuse devices that support receiving non-SSP A-MSDU frames—which is mandatory as part of 802.11n—to inject arbitrary network packets.

This vulnerability is part of a collection of Wi-Fi security flaws collectively known as "FragAttacks" (fragmentation and aggregation attacks), which affect virtually all Wi-Fi devices due to their origin in the 802.11 standard itself.

Critical Impact

An attacker within adjacent network range can inject arbitrary network packets by exploiting the unauthenticated A-MSDU flag, potentially bypassing Wi-Fi security protections including WPA3.

Affected Products

• IEEE 802.11 Standard (all implementations supporting non-SSP A-MSDU frames)
• Linux Kernel (mac80211 subsystem)
• Microsoft Windows 7, 8.1, 10 and Windows Server 2008/2012/2016/2019
• Debian Linux
• Cisco Aironet, Catalyst, and Meraki access points
• Intel Wi-Fi 6 and AC wireless adapters
• Siemens SCALANCE wireless access points
• Arista wireless products

Discovery Timeline

• May 11, 2021 - CVE-2020-24588 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-24588

Vulnerability Analysis

The vulnerability stems from a fundamental design flaw in the IEEE 802.11 wireless networking standard. In 802.11n and later implementations, Aggregate MAC Service Data Units (A-MSDUs) are used to improve efficiency by combining multiple data frames into a single transmission. The A-MSDU flag, which indicates whether a frame contains aggregated data, is stored in the plaintext QoS header field and is not protected by the cryptographic authentication mechanisms (such as those provided by WPA/WPA2/WPA3).

Because this flag is not authenticated, an adversary can manipulate it to change how a Wi-Fi device interprets received frames. Specifically, an attacker can set the A-MSDU flag on a non-aggregated frame, causing the receiving device to parse the frame's contents as multiple subframes—effectively allowing the injection of arbitrary network packets that appear to originate from a trusted source.

Root Cause

The root cause is classified as CWE-327 (Use of a Broken or Risky Cryptographic Algorithm). The IEEE 802.11 standard specification does not mandate authentication of the A-MSDU flag in the QoS header field, leaving this critical indicator unprotected. This design decision, made years ago for performance and compatibility reasons, creates an inherent weakness that cannot be fully addressed without modifying the standard itself.

The vulnerability affects all devices supporting non-SSP (non-Signaling and Payload Protected) A-MSDU frames, which is a mandatory feature for 802.11n compliance. This means virtually every modern Wi-Fi device is potentially affected.

Attack Vector

The attack requires the adversary to be within wireless range of the target device (adjacent network access). The attacker does not need valid network credentials or user interaction to exploit this vulnerability. The attack can be executed by:

1. Capturing legitimate Wi-Fi traffic between the access point and client
2. Modifying the A-MSDU flag in captured frames
3. Injecting the modified frames with malicious subframe content
4. The receiving device processes the injected packets as legitimate traffic

The injected packets can be used for various malicious purposes, including DNS spoofing, TCP connection hijacking, or exfiltrating data from isolated network segments.

Detection Methods for CVE-2020-24588

Indicators of Compromise

• Unexpected A-MSDU frames being received with unusual subframe structures
• Network traffic anomalies indicating injected packets from unexpected sources
• DNS responses or other network data that doesn't match expected patterns
• Wireless intrusion detection systems flagging unusual frame aggregation behavior

Detection Strategies

• Deploy wireless intrusion detection/prevention systems (WIDS/WIPS) capable of monitoring 802.11 frame structures
• Implement network traffic analysis to detect anomalous packet injection patterns
• Monitor for unexpected DNS responses or ARP traffic that could indicate packet injection
• Enable enhanced logging on wireless access points to track A-MSDU frame handling

Monitoring Recommendations

• Configure wireless infrastructure monitoring to alert on abnormal frame aggregation patterns
• Implement network segmentation monitoring to detect cross-segment packet injection attempts
• Deploy endpoint detection solutions that can identify unusual network behavior resulting from injected packets
• Conduct regular wireless security assessments to identify vulnerable devices in your environment

How to Mitigate CVE-2020-24588

Immediate Actions Required

• Apply firmware and driver updates from affected vendors (Microsoft, Intel, Cisco, Siemens, Arista, Linux distributions)
• Review vendor security advisories for specific mitigation guidance
• Consider network segmentation to limit the impact of potential packet injection attacks
• Implement additional network-layer security controls (DNSSEC, encrypted DNS, HTTPS) to reduce injection impact

Patch Information

Multiple vendors have released patches and firmware updates to address this vulnerability:

• Microsoft: Security updates available for Windows 7 SP1 through Windows 10 and Windows Server editions
• Linux: Patches available for the mac80211 kernel subsystem; see Debian LTS Security Announcements for distribution-specific guidance
• Cisco: See the Cisco Security Advisory for affected products and updates
• Intel: Updated Wi-Fi drivers available per Intel Security Advisory INTEL-SA-00473
• Siemens: See Siemens Security Advisory SSA-913875 for SCALANCE device updates
• Arista: See Arista Security Advisory 12602 for affected products

Workarounds

• Disable A-MSDU reception where supported by the device firmware (may impact performance)
• Implement strict network segmentation to contain potential injection attacks
• Use application-layer encryption (TLS/HTTPS) for all sensitive communications to protect against injected packets
• Deploy VPN solutions for additional encryption layer over wireless connections

# Linux: Check kernel version and update if necessary
uname -r
# Update to patched kernel version
sudo apt update && sudo apt upgrade linux-image-$(uname -r)

# Verify wireless driver version for Intel adapters
modinfo iwlwifi | grep version