CVE-2025-37752 net_sched: sch_sfq: move the limit validation

What is CVE-2025-37752?

CVE-2025-37752 is a high-severity vulnerability in Debian Debian Linux, published on 1 May 2025. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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

net_sched: sch_sfq: move the limit validation

It is not sufficient to directly validate the limit on the data that the user passes as it can be updated based on how the other parameters are changed.

Move the check at the end of the configuration update process to also catch scenarios where the limit is indirectly updated, for example with the following configurations:

tc qdisc add dev dummy0 handle 1: root sfq limit 2 flows 1 depth 1 tc qdisc add dev dummy0 handle 1: root sfq limit 2 flows 1 divisor 1

This fixes the following syzkaller reported crash:

------------[ cut here ]------------ UBSAN: array-index-out-of-bounds in net/sched/sch_sfq.c:203:6 index 65535 is out of range for type 'struct sfq_head[128]' CPU: 1 UID: 0 PID: 3037 Comm: syz.2.16 Not tainted 6.14.0-rc2-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024 Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x201/0x300 lib/dump_stack.c:120 ubsan_epilogue lib/ubsan.c:231 [inline] __ubsan_handle_out_of_bounds+0xf5/0x120 lib/ubsan.c:429 sfq_link net/sched/sch_sfq.c:203 [inline] sfq_dec+0x53c/0x610 net/sched/sch_sfq.c:231 sfq_dequeue+0x34e/0x8c0 net/sched/sch_sfq.c:493 sfq_reset+0x17/0x60 net/sched/sch_sfq.c:518 qdisc_reset+0x12e/0x600 net/sched/sch_generic.c:1035 tbf_reset+0x41/0x110 net/sched/sch_tbf.c:339 qdisc_reset+0x12e/0x600 net/sched/sch_generic.c:1035 dev_reset_queue+0x100/0x1b0 net/sched/sch_generic.c:1311 netdev_for_each_tx_queue include/linux/netdevice.h:2590 [inline] dev_deactivate_many+0x7e5/0xe70 net/sched/sch_generic.c:1375

Weakness: CWE-129

Which versions are affected by CVE-2025-37752?

It affects 2 products.

Products include Debian Debian Linux, Linux kernel.

How do I fix CVE-2025-37752?

Apply the vendor's patch.

Is CVE-2025-37752 being exploited?

There is no known exploitation of CVE-2025-37752 in the wild and no public exploit code.

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All Debian Debian Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2025-37752, DEBIAN-CVE-2025-37752, GHSA-39cv-hx7c-vjcq, ROOT-OS-DEBIAN-12-CVE-2025-37752, ROOT-OS-UBUNTU-2204-CVE-2025-37752, ROOT-OS-UBUNTU-2404-CVE-2025-37752 and 3 more.