PT-2026-52304 · Linux · Linux

Publicado 2026-06-25 · Atualizado 2026-06-25 · CVE-2026-53208

NVD

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: L2CAP: reject BR/EDR signaling packets over MTUsig

net/bluetooth/l2cap core.c:l2cap sig channel() accepts BR/EDR signaling packets up to the channel MTU and dispatches each command without enforcing the signaling MTU (MTUsig). A Bluetooth BR/EDR peer within radio range can send a fixed-channel CID 0x0001 packet that is larger than MTUsig and contains many L2CAP ECHO REQ commands before pairing. In a real-radio stock-kernel run, one 681-byte signaling packet containing 168 zero-length ECHO REQ commands made the target transmit 168 ECHO RSP frames over about 220 ms.

Impact: a Bluetooth BR/EDR peer within radio range, before pairing, can force 168 ECHO RSP frames from one 681-byte fixed-channel signaling packet containing packed ECHO REQ commands.

Define Linux's BR/EDR signaling MTU as the spec minimum of 48 bytes and reject any larger signaling packet with one L2CAP COMMAND REJECT RSP carrying L2CAP REJ MTU EXCEEDED before any command is dispatched.

The Bluetooth Core spec wording for MTUExceeded says the reject identifier shall match the first request command in the packet, and that packets containing only responses shall be silently discarded. Linux intentionally deviates from that prescription: silently discarding desynchronizes the peer because the remote stack never learns its responses were dropped, and locating the first request command requires walking command headers past MTUsig, i.e. processing bytes from a packet we have already decided is too large to process. We therefore always emit one reject and use the identifier from the first command header, a single fixed-offset byte read.

The unrestricted BR/EDR signaling parser and ECHO REQ response path both trace to the initial git import; no later introducing commit is available for a Fixes tag.

Identificadores relacionados

CVE-2026-53208

Produtos afetados

Linux

Referências · 9

• https://git.kernel.org/stable/c/dd214733544427587a95f66dbf3adff072568990 · Nota
• https://git.kernel.org/stable/c/e2b8acf9405bd9b1baf1c54dc897b0905db689bf · Nota
• https://git.kernel.org/stable/c/214a2042b16b3c8d798a8b9ef9f36094f13a9859 · Nota
• https://git.kernel.org/stable/c/e05c4ac575b457978a7ef441053394169084869c · Nota
• https://git.kernel.org/stable/c/dedc92b96dc1d8919a3bdf2495ede68922ef7ebc · Nota
• https://nvd.nist.gov/vuln/detail/CVE-2026-53208 · Nota de Segurança
• https://git.kernel.org/stable/c/fa5823126239b3e453fac1a2fe50726c7f4a55e1 · Nota
• https://git.kernel.org/stable/c/a8335f3db15bd1e0e82e0db5d488fabc7d10d1ab · Nota
• https://git.kernel.org/stable/c/b20e8a98dd29b121f58fcdf51e8576119aba536a · Nota