CVE-2026-98602 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: bnep: fix out-of-bounds reads on short RX/TX frames and control fallthrough
Fix multiple out-of-bounds reads in Bluetooth BNEP frame processing:
1. In bnep_rx_frame() and bnep_ctrl_frame() (net/bluetooth/bnep/core.c), use pskb_may_pull() to verify the BNEP header, control type byte, filter count, and extension headers exist before reading them, and return 0 after handling BNEP_CONTROL instead of falling through to Ethernet frame submission when no extension headers follow. 2. In bnep_net_xmit() (net/bluetooth/bnep/netdev.c), verify skb->len >= ETH_HLEN with pskb_may_pull() before reading the 14-byte Ethernet header to prevent an out-of-bounds heap read and infoleak on short AF_PACKET TX frames.
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Analysis
by VulDB Data Team • 10/18/2026
The Linux kernel Bluetooth Network Encapsulation Protocol implementation contained critical memory safety vulnerabilities that allowed for out-of-bounds reads, potentially leading to information disclosure or system instability. These flaws were located within the BNEP core processing logic and network device transmission routines, specifically affecting how short receive and transmit frames are handled. The vulnerability stems from insufficient validation of packet buffer lengths before accessing specific header fields, a common issue in low-level networking code where malformed packets can trigger unintended memory access patterns.
In the bnep_rx_frame and bnep_ctrl_frame functions within net/bluetooth/bnep/core.c, the kernel failed to adequately verify that all necessary BNEP headers were present in the received packet buffer before attempting to read them. Specifically, the code did not ensure the existence of the BNEP header itself, the control type byte, the filter count field, or any extension headers prior to dereferencing these memory locations. This lack of boundary checking meant that if a peer device sent a truncated frame lacking these expected structures, the kernel would read beyond the allocated buffer boundaries. Such out-of-bounds reads can expose sensitive kernel memory contents to an attacker who controls the Bluetooth connection, facilitating information leakage attacks where internal system data is extracted through crafted malicious packets.
Furthermore, the bnep_ctrl_frame function exhibited a control flow error known as fallthrough behavior. After handling BNEP_CONTROL messages, the code failed to return immediately and instead continued execution into the logic responsible for submitting Ethernet frames. This logical flaw occurs when no extension headers follow the control message, causing the kernel to misinterpret the packet structure and attempt to process it as a standard Ethernet frame despite its actual nature being a control command. This incorrect processing path can lead to further memory corruption or unexpected behavior within the networking stack, compounding the risks associated with the initial out-of-bounds read vulnerabilities by introducing unpredictable state transitions in the protocol handler.
A separate but related vulnerability existed in the bnep_net_xmit function located in net/bluetooth/bnep/netdev.c, which handles outgoing network traffic. This routine was responsible for transmitting data over AF_PACKET interfaces using Bluetooth BNEP encapsulation. The code attempted to read a standard 14-byte Ethernet header from the socket buffer without first verifying that the buffer contained at least ETH_HLEN bytes of data. When processing short transmit frames where the length was less than the required Ethernet header size, this operation resulted in an out-of-bounds heap read. This flaw allows for information disclosure as the kernel reads uninitialized or adjacent memory to fill the missing header fields, potentially leaking stack variables or other sensitive kernel structures to remote attackers who can influence the transmission parameters.
These vulnerabilities are classified under CWE-125, which describes Out-of-Bounds Read, and align with MITRE ATT&CK techniques related to Collection via Network Capture and Data from Information Repositories if exploited for information gathering. The root cause is a failure in input validation and boundary checking within critical networking subsystems, highlighting the importance of rigorous packet length verification before any memory access operations in kernel-space drivers. Attackers could exploit these flaws by establishing Bluetooth connections and sending specially crafted short frames that trigger the out-of-bounds reads or control flow errors, thereby gaining unauthorized insight into system memory states without requiring authentication on some configurations depending on local network exposure.
To mitigate these risks, users must apply the latest security patches provided by their Linux distribution vendors which include fixes for the BNEP subsystem. The patch addresses the issues by implementing proper use of pskb_may_pull to verify packet availability before accessing header fields and correcting the control flow in bnep_ctrl_frame to prevent fallthrough execution after handling control messages. Administrators should ensure that Bluetooth services are updated and consider restricting Bluetooth device discovery or pairing if not actively required, thereby reducing the attack surface for potential exploitation via crafted wireless packets. Regular kernel updates remain the primary defense against such low-level memory safety vulnerabilities in network protocol implementations.