# CVE-2022-49958: net/sched: fix netdevice reference leaks in attach_default_qdiscs()

> A reference leak in the Linux kernel network scheduler can cause resource exhaustion and denial of service when qdisc attachment fails.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 18 Jun 2025
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2022-49958, GHSA-84fm-g3cv-66r3, UBUNTU-CVE-2022-49958

## What is CVE-2022-49958?

CVE-2022-49958 is a medium-severity memory corruption vulnerability in Linux kernel, published on 18 Jun 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: fix netdevice reference leaks in attach_default_qdiscs()

In attach_default_qdiscs(), if a dev has multiple queues and queue 0 fails
to attach qdisc because there is no memory in attach_one_default_qdisc().
Then dev->qdisc will be noop_qdisc by default. But the other queues may be
able to successfully attach to default qdisc.

In this case, the fallback to noqueue process will be triggered. If the
original attached qdisc is not released and a new one is directly
attached, this will cause netdevice reference leaks.

The following is the bug log:

veth0: default qdisc (fq_codel) fail, fallback to noqueue
unregister_netdevice: waiting for veth0 to become free. Usage count = 32
leaked reference.
 qdisc_alloc+0x12e/0x210
 qdisc_create_dflt+0x62/0x140
 attach_one_default_qdisc.constprop.41+0x44/0x70
 dev_activate+0x128/0x290
 __dev_open+0x12a/0x190
 __dev_change_flags+0x1a2/0x1f0
 dev_change_flags+0x23/0x60
 do_setlink+0x332/0x1150
 __rtnl_newlink+0x52f/0x8e0
 rtnl_newlink+0x43/0x70
 rtnetlink_rcv_msg+0x140/0x3b0
 netlink_rcv_skb+0x50/0x100
 netlink_unicast+0x1bb/0x290
 netlink_sendmsg+0x37c/0x4e0
 sock_sendmsg+0x5f/0x70
 ____sys_sendmsg+0x208/0x280

Fix this bug by clearing any non-noop qdiscs that may have been assigned
before trying to re-attach.

## Which versions are affected by CVE-2022-49958?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2022-49958?

Apply the vendor's patch.

## Is CVE-2022-49958 being exploited?

There is no known exploitation of CVE-2022-49958 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2022-49958 and fix it if it is affected.

What it is: CVE-2022-49958 is a medium-severity memory corruption vulnerability in Linux kernel, published on 18 Jun 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-2022-49958 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2022-49958/ (Markdown: https://insights.sbomify.com/CVE-2022-49958/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2022-49958
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2022-49958
- OSV: https://osv.dev/vulnerability/CVE-2022-49958

---
From sbomify Insights: https://insights.sbomify.com/CVE-2022-49958/
Summaries are generated and may contain mistakes; the official description above is the record.