Bug 2555106 (CVE-2026-98733)

Summary:	CVE-2026-98733 kernel: kernel: Denial of Service via use-after-free in Bluetooth ISO packet queueing
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	rhel-process-autobot, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel's Bluetooth subsystem. Inadequate synchronization when handling fragmented isochronous (ISO) data packets allows a race condition between packet queueing and transmission operations. A local user could exploit this flaw to trigger a use-after-free condition, leading to a system crash and Denial of Service (DoS).	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-10-18 15:54:48 UTC

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

Bluetooth: hci_core: Serialize fragmented ISO packet queueing

The fragmented path in hci_queue_iso() calls __skb_queue_tail() without
holding conn->data_q.lock. The socket lock serializes senders, but the
transmit worker can concurrently remove packets from this queue using
skb_dequeue().

After an insertion saves the old tail pointer, hci_sched_iso() can dequeue
that packet and pass it to the driver. The driver can free the packet
before the insertion resumes and writes to the old tail's next pointer,
causing a use-after-free. Concurrent updates can also corrupt the queue.

KASAN reported:

  BUG: KASAN: slab-use-after-free in hci_send_iso+0xc7d/0xe10
  Call Trace:
   hci_send_iso+0xc7d/0xe10
   iso_sock_sendmsg+0x710/0x900
   __sys_sendto+0x34a/0x3a0

  Allocated by task 86:
   __alloc_skb+0xdd/0x820
   alloc_skb_with_frags+0x7e/0x770
   sock_alloc_send_pskb+0x67a/0x820
   bt_skb_sendmsg.constprop.0+0xc0/0x6c0
   iso_sock_sendmsg+0x44e/0x900

  Freed by task 90:
   kmem_cache_free+0xcb/0x3d0
   vhci_read+0x33f/0x4d0
   vfs_read+0x177/0xa20

Hold the queue lock across the entire fragment batch, as hci_queue_acl()
does, to serialize insertion against dequeue while preserving fragment
ordering.