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

> A local attacker can trigger a kernel crash via specific traffic control configurations due to improper limit validation in the SFQ scheduler.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 May 2025
- **Updated:** 5 Aug 2026
- **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, SUSE-SU-2025:02626-1, SUSE-SU-2025:02699-1, UBUNTU-CVE-2025-37752

## 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 (Improper Validation of Array Index)

## Which versions are affected by CVE-2025-37752?

It affects 2 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `kernel-livepatch-SLE15-SP6-RT_Update_11` | SUSE:Linux Enterprise Live Patching 15 SP6 | All versions | 2-150600.2.1 |
| `kernel-livepatch-SLE15-SP6_Update_12` | SUSE:Linux Enterprise Live Patching 15 SP6 | All versions | 2-150600.2.1 |

Products: 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.

## Other vulnerabilities in Debian Debian Linux

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- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-37752 and fix it if it is affected.

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

Affected product: Debian Debian Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-37752/ (Markdown: https://insights.sbomify.com/CVE-2025-37752/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-37752
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-37752
- OSV: https://osv.dev/vulnerability/CVE-2025-37752

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-37752/
Summaries are generated and may contain mistakes; the official description above is the record.