Bug 2517013 (CVE-2026-74540)

Summary: CVE-2026-74540 kernel: Bluetooth: L2CAP: fix UAF in l2cap_le_connect_rsp
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Bluetooth L2CAP (Logical Link Control and Adaptation Protocol) component. A use-after-free (UAF) vulnerability exists in the `l2cap_le_connect_rsp()` function, where a channel can be freed while still being referenced. This can be triggered by a remote disconnect, potentially allowing a remote attacker to corrupt memory and achieve arbitrary code execution or cause a denial of service.
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Description OSIDB Bzimport 2026-08-15 12:44:36 UTC 
In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: L2CAP: fix UAF in l2cap_le_connect_rsp

l2cap_le_connect_rsp() obtains a channel via
__l2cap_get_chan_by_ident() but neither holds a reference nor uses
l2cap_chan_hold_unless_zero() before locking and operating on it.
A concurrent l2cap_chan_del() triggered by a remote disconnect can
free the channel between the lookup and l2cap_chan_lock(), causing
a use-after-free.

The BR/EDR counterpart l2cap_connect_rsp() and the sibling handler
l2cap_le_command_rej() already use l2cap_chan_hold_unless_zero()
to safely hold a reference, but l2cap_le_connect_rsp() was left
unprotected.

Fix by adding l2cap_chan_hold_unless_zero() after the ident lookup
and l2cap_chan_put() on the exit path, consistent with other L2CAP
response handlers.
Comment 1 gkamathe 2026-08-21 10:55:02 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081548-CVE-2026-74540-5b1d@gregkh/T