vulnerability
Amazon Linux 2023: CVE-2025-38037: Important priority package update for kernel (Multiple Advisories)
| Severity | CVSS | Published | Added | Modified |
|---|---|---|---|---|
| 1 | (AV:L/AC:M/Au:M/C:N/I:N/A:P) | Jun 18, 2025 | Jul 11, 2025 | Dec 4, 2025 |
Severity
1
CVSS
(AV:L/AC:M/Au:M/C:N/I:N/A:P)
Published
Jun 18, 2025
Added
Jul 11, 2025
Modified
Dec 4, 2025
Description
In the Linux kernel, the following vulnerability has been resolved:
vxlan: Annotate FDB data races
The 'used' and 'updated' fields in the FDB entry structure can be
accessed concurrently by multiple threads, leading to reports such as
[1]. Can be reproduced using [2].
Suppress these reports by annotating these accesses using
READ_ONCE() / WRITE_ONCE().
[1]
BUG: KCSAN: data-race in vxlan_xmit / vxlan_xmit
write to 0xffff942604d263a8 of 8 bytes by task 286 on cpu 0:
vxlan_xmit+0xb29/0x2380
dev_hard_start_xmit+0x84/0x2f0
__dev_queue_xmit+0x45a/0x1650
packet_xmit+0x100/0x150
packet_sendmsg+0x2114/0x2ac0
__sys_sendto+0x318/0x330
__x64_sys_sendto+0x76/0x90
x64_sys_call+0x14e8/0x1c00
do_syscall_64+0x9e/0x1a0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
read to 0xffff942604d263a8 of 8 bytes by task 287 on cpu 2:
vxlan_xmit+0xadf/0x2380
dev_hard_start_xmit+0x84/0x2f0
__dev_queue_xmit+0x45a/0x1650
packet_xmit+0x100/0x150
packet_sendmsg+0x2114/0x2ac0
__sys_sendto+0x318/0x330
__x64_sys_sendto+0x76/0x90
x64_sys_call+0x14e8/0x1c00
do_syscall_64+0x9e/0x1a0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
value changed: 0x00000000fffbac6e -> 0x00000000fffbac6f
Reported by Kernel Concurrency Sanitizer on:
CPU: 2 UID: 0 PID: 287 Comm: mausezahn Not tainted 6.13.0-rc7-01544-gb4b270f11a02 #5
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014
[2]
#!/bin/bash
set +H
echo whitelist > /sys/kernel/debug/kcsan
echo !vxlan_xmit > /sys/kernel/debug/kcsan
ip link add name vx0 up type vxlan id 10010 dstport 4789 local 192.0.2.1
bridge fdb add 00:11:22:33:44:55 dev vx0 self static dst 198.51.100.1
taskset -c 0 mausezahn vx0 -a own -b 00:11:22:33:44:55 -c 0 -q &
taskset -c 2 mausezahn vx0 -a own -b 00:11:22:33:44:55 -c 0 -q &
vxlan: Annotate FDB data races
The 'used' and 'updated' fields in the FDB entry structure can be
accessed concurrently by multiple threads, leading to reports such as
[1]. Can be reproduced using [2].
Suppress these reports by annotating these accesses using
READ_ONCE() / WRITE_ONCE().
[1]
BUG: KCSAN: data-race in vxlan_xmit / vxlan_xmit
write to 0xffff942604d263a8 of 8 bytes by task 286 on cpu 0:
vxlan_xmit+0xb29/0x2380
dev_hard_start_xmit+0x84/0x2f0
__dev_queue_xmit+0x45a/0x1650
packet_xmit+0x100/0x150
packet_sendmsg+0x2114/0x2ac0
__sys_sendto+0x318/0x330
__x64_sys_sendto+0x76/0x90
x64_sys_call+0x14e8/0x1c00
do_syscall_64+0x9e/0x1a0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
read to 0xffff942604d263a8 of 8 bytes by task 287 on cpu 2:
vxlan_xmit+0xadf/0x2380
dev_hard_start_xmit+0x84/0x2f0
__dev_queue_xmit+0x45a/0x1650
packet_xmit+0x100/0x150
packet_sendmsg+0x2114/0x2ac0
__sys_sendto+0x318/0x330
__x64_sys_sendto+0x76/0x90
x64_sys_call+0x14e8/0x1c00
do_syscall_64+0x9e/0x1a0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
value changed: 0x00000000fffbac6e -> 0x00000000fffbac6f
Reported by Kernel Concurrency Sanitizer on:
CPU: 2 UID: 0 PID: 287 Comm: mausezahn Not tainted 6.13.0-rc7-01544-gb4b270f11a02 #5
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014
[2]
#!/bin/bash
set +H
echo whitelist > /sys/kernel/debug/kcsan
echo !vxlan_xmit > /sys/kernel/debug/kcsan
ip link add name vx0 up type vxlan id 10010 dstport 4789 local 192.0.2.1
bridge fdb add 00:11:22:33:44:55 dev vx0 self static dst 198.51.100.1
taskset -c 0 mausezahn vx0 -a own -b 00:11:22:33:44:55 -c 0 -q &
taskset -c 2 mausezahn vx0 -a own -b 00:11:22:33:44:55 -c 0 -q &
Solutions
amazon-linux-2023-upgrade-bpftoolamazon-linux-2023-upgrade-bpftool-debuginfoamazon-linux-2023-upgrade-kernelamazon-linux-2023-upgrade-kernel6-12amazon-linux-2023-upgrade-kernel6-12-debuginfoamazon-linux-2023-upgrade-kernel6-12-debuginfo-common-aarch64amazon-linux-2023-upgrade-kernel6-12-debuginfo-common-x86-64amazon-linux-2023-upgrade-kernel6-12-modules-extraamazon-linux-2023-upgrade-kernel-debuginfoamazon-linux-2023-upgrade-kernel-debuginfo-common-aarch64amazon-linux-2023-upgrade-kernel-debuginfo-common-x86-64amazon-linux-2023-upgrade-kernel-develamazon-linux-2023-upgrade-kernel-headersamazon-linux-2023-upgrade-kernel-libbpfamazon-linux-2023-upgrade-kernel-libbpf-debuginfoamazon-linux-2023-upgrade-kernel-libbpf-develamazon-linux-2023-upgrade-kernel-libbpf-staticamazon-linux-2023-upgrade-kernel-livepatch-6-1-141-155-222amazon-linux-2023-upgrade-kernel-livepatch-6-12-25-32-101amazon-linux-2023-upgrade-kernel-livepatch-6-12-29-33-102amazon-linux-2023-upgrade-kernel-livepatch-6-12-30-34-92amazon-linux-2023-upgrade-kernel-livepatch-6-12-31-35-92amazon-linux-2023-upgrade-kernel-modules-extraamazon-linux-2023-upgrade-kernel-modules-extra-commonamazon-linux-2023-upgrade-kernel-toolsamazon-linux-2023-upgrade-kernel-tools-debuginfoamazon-linux-2023-upgrade-kernel-tools-develamazon-linux-2023-upgrade-perfamazon-linux-2023-upgrade-perf6-12amazon-linux-2023-upgrade-perf6-12-debuginfoamazon-linux-2023-upgrade-perf-debuginfoamazon-linux-2023-upgrade-python3-perfamazon-linux-2023-upgrade-python3-perf6-12amazon-linux-2023-upgrade-python3-perf6-12-debuginfoamazon-linux-2023-upgrade-python3-perf-debuginfo
References
- CVE-2025-38037
- https://attackerkb.com/topics/CVE-2025-38037
- URL-https://alas.aws.amazon.com/AL2023/ALAS-2025-1037.html
- URL-https://alas.aws.amazon.com/AL2023/ALAS-2025-1052.html
- URL-https://alas.aws.amazon.com/AL2023/ALASLIVEPATCH-2025-052.html
- URL-https://alas.aws.amazon.com/AL2023/ALASLIVEPATCH-2025-053.html
- URL-https://alas.aws.amazon.com/AL2023/ALASLIVEPATCH-2025-054.html
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