CVE-2026-72333
Received Received - Intake

Bluetooth: L2CAP ident leak in Linux kernel

Publication date: 2026-08-15

Last updated on: 2026-08-15

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: fix tx ident leak for commands without a response Commit 6c3ea155e5ee ("Bluetooth: L2CAP: Fix not tracking outstanding TX ident") changed ident allocation to use an IDA, releasing idents in l2cap_put_ident() when the matching response command is received. But identifiers allocated for commands that have no response defined are never released. In particular L2CAP_LE_CREDITS is sent repeatedly for the lifetime of an LE CoC channel, so a peer streaming data to the host exhausts the 1-255 ident range after 254 credit packets. From then on l2cap_get_ident() fails: kernel: Bluetooth: Unable to allocate ident: -28 and every subsequent L2CAP_LE_CREDITS packet is sent with ident 0, which is invalid (Core Spec, Vol 3, Part A, Section 4: "Signaling identifier 0x00 is an invalid identifier and shall never be used in any command"). Remote stacks that validate the ident drop these commands, never receive new credits, and the channel stalls permanently. With default socket buffers this happens after roughly 0.5 MB of received data (the exact amount depends on the socket receive buffer): < ACL Data TX: Handle 2048 flags 0x00 dlen 12 LE L2CAP: LE Flow Control Credit (0x16) ident 0 len 4 Source CID: 64 Credits: 1 Release the ident immediately after sending L2CAP_LE_CREDITS since no response will ever release it. Use a local variable instead of chan->ident so that an ident that an EXT_FLOWCTL channel may be waiting on (e.g. a pending reconfigure) is not overwritten by a credit packet. Also add the missing L2CAP_LE_CONN_RSP case to l2cap_put_ident() so idents allocated for outgoing L2CAP_LE_CONN_REQ commands are released when the response arrives.

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Meta Information

Published
2026-08-15
Last Modified
2026-08-15
Generated
2026-08-15
AI Q&A
2026-08-15
EPSS Evaluated
N/A
NVD
CVE-2026-72333
EUVD
EUVD-2026-59232

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a memory leak in the Bluetooth L2CAP layer. When sending certain Bluetooth commands without responses, like L2CAP_LE_CREDITS, the system fails to release allocated identifiers. This causes the identifier pool to exhaust, leading to failures in subsequent commands and potential channel stalls.

Detection Guidance

This vulnerability may manifest as Bluetooth connection failures or stalled channels after receiving approximately 0.5 MB of data. Check kernel logs for messages like 'Bluetooth: Unable to allocate ident: -28' or 'ident 0' in L2CAP_LE_CREDITS packets. Monitor Bluetooth subsystem errors using 'dmesg | grep Bluetooth' or 'journalctl -k | grep Bluetooth'.

Impact Analysis

This vulnerability can cause Bluetooth connections to fail after transferring roughly 0.5 MB of data. It may lead to permanent stalls in Bluetooth channels, disrupting data transfers and communication between devices.

Mitigation Strategies

Apply the Linux kernel patch referenced in the CVE description (commit 6c3ea155e5ee). Update to a kernel version containing this fix. If immediate patching is not possible, restrict Bluetooth usage to trusted devices or disable Bluetooth functionality until patched.

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