Summary
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: Fix slab...
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: L2CAP: Fix slab-use-after-free Read in l2cap_send_cmd
After the hci sync command releases l2cap_conn, the hci receive data work
queue references the released l2cap_conn when sending to the upper layer.
Add hci dev lock to the hci receive data work queue to synchronize the two.
[1]
BUG: KASAN: slab-use-after-free in l2cap_send_cmd+0x187/0x8d0 net/bluetooth/l2cap_core.c:954
Read of size 8 at addr ffff8880271a4000 by task kworker/u9:2/5837
CPU: 0 UID: 0 PID: 5837 Comm: kworker/u9:2 Not tainted 6.13.0-rc5-syzkaller-00163-gab75170520d4 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Workqueue: hci1 hci_rx_work
Call Trace:
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0x169/0x550 mm/kasan/report.c:489
kasan_report+0x143/0x180 mm/kasan/report.c:602
l2cap_build_cmd net/bluetooth/l2cap_core.c:2964 [inline]
l2cap_send_cmd+0x187/0x8d0 net/bluetooth/l2cap_core.c:954
l2cap_sig_send_rej net/bluetooth/l2cap_core.c:5502 [inline]
l2cap_sig_channel net/bluetooth/l2cap_core.c:5538 [inline]
l2cap_recv_frame+0x221f/0x10db0 net/bluetooth/l2cap_core.c:6817
hci_acldata_packet net/bluetooth/hci_core.c:3797 [inline]
hci_rx_work+0x508/0xdb0 net/bluetooth/hci_core.c:4040
process_one_work kernel/workqueue.c:3229 [inline]
process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310
worker_thread+0x870/0xd30 kernel/workqueue.c:3391
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
Allocated by task 5837:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
__kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:394
kasan_kmalloc include/linux/kasan.h:260 [inline]
__kmalloc_cache_noprof+0x243/0x390 mm/slub.c:4329
kmalloc_noprof include/linux/slab.h:901 [inline]
kzalloc_noprof include/linux/slab.h:1037 [inline]
l2cap_conn_add+0xa9/0x8e0 net/bluetooth/l2cap_core.c:6860
l2cap_connect_cfm+0x115/0x1090 net/bluetooth/l2cap_core.c:7239
hci_connect_cfm include/net/bluetooth/hci_core.h:2057 [inline]
hci_remote_features_evt+0x68e/0xac0 net/bluetooth/hci_event.c:3726
hci_event_func net/bluetooth/hci_event.c:7473 [inline]
hci_event_packet+0xac2/0x1540 net/bluetooth/hci_event.c:7525
hci_rx_work+0x3f3/0xdb0 net/bluetooth/hci_core.c:4035
process_one_work kernel/workqueue.c:3229 [inline]
process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310
worker_thread+0x870/0xd30 kernel/workqueue.c:3391
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
Freed by task 54:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:582
poison_slab_object mm/kasan/common.c:247 [inline]
__kasan_slab_free+0x59/0x70 mm/kasan/common.c:264
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2353 [inline]
slab_free mm/slub.c:4613 [inline]
kfree+0x196/0x430 mm/slub.c:4761
l2cap_connect_cfm+0xcc/0x1090 net/bluetooth/l2cap_core.c:7235
hci_connect_cfm include/net/bluetooth/hci_core.h:2057 [inline]
hci_conn_failed+0x287/0x400 net/bluetooth/hci_conn.c:1266
hci_abort_conn_sync+0x56c/0x11f0 net/bluetooth/hci_sync.c:5603
hci_cmd_sync_work+0x22b/0x400 net/bluetooth/hci_sync.c:332
process_one_work kernel/workqueue.c:3229 [inline]
process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310
worker_thread+0x870/0xd30 kernel/workqueue.c:3391
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entr
---truncated---
Impact
Memory is accessed after it has been freed, leading to undefined behavior in native code. Typical impact: memory corruption, crash, or potential code execution.
CVE-2025-21969 has a CVSS score of 7.8 (High). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2025-21969? CVE-2025-21969 is a high-severity use after free vulnerability. No fixed version is listed yet. Memory is accessed after it has been freed, leading to undefined behavior in native code.
- How severe is CVE-2025-21969? CVE-2025-21969 has a CVSS score of 7.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Is there a fix for CVE-2025-21969? No fixed version is listed for CVE-2025-21969 yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is CVE-2025-21969 exploitable, and should I be worried? Whether CVE-2025-21969 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-21969 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.