# CVE-2026-45845: net/sched: taprio: fix NULL pointer dereference in class dump

> An unprivileged local user can cause a kernel panic via NULL pointer dereference in the TAPRIO qdisc class dump path.

- **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:** 27 May 2026
- **Updated:** 14 Jun 2026
- **Also known as:** AZL-88506, BELL-CVE-2026-45845, DEBIAN-CVE-2026-45845, GHSA-656f-mgf3-p7r2, ROOT-OS-DEBIAN-13-CVE-2026-45845, ROOT-OS-UBUNTU-2404-CVE-2026-45845, UBUNTU-CVE-2026-45845

## What is CVE-2026-45845?

CVE-2026-45845 is a medium-severity vulnerability in Linux kernel, published on 27 May 2026. 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: taprio: fix NULL pointer dereference in class dump

When a TAPRIO child qdisc is deleted via RTM_DELQDISC, taprio_graft()
is called with new == NULL and stores NULL into q->qdiscs[cl - 1].
Subsequent RTM_GETTCLASS dump operations walk all classes via
taprio_walk() and call taprio_dump_class(), which calls taprio_leaf()
returning the NULL pointer, then dereferences it to read child->handle,
causing a kernel NULL pointer dereference.

The bug is reachable with namespace-scoped CAP_NET_ADMIN on any kernel
with CONFIG_NET_SCH_TAPRIO enabled. On systems with unprivileged user
namespaces enabled, an unprivileged local user can trigger a kernel
panic by creating a taprio qdisc inside a new network namespace,
grafting an explicit child qdisc, deleting it, and requesting a class
dump. The RTM_GETTCLASS dump itself requires no capability.

 Oops: general protection fault, probably for non-canonical address 0xdffffc0000000007: 0000 [#1] SMP KASAN NOPTI
 KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]
 RIP: 0010:taprio_dump_class (net/sched/sch_taprio.c:2478)
 Call Trace:
  <TASK>
  tc_fill_tclass (net/sched/sch_api.c:1966)
  qdisc_class_dump (net/sched/sch_api.c:2326)
  taprio_walk (net/sched/sch_taprio.c:2514)
  tc_dump_tclass_qdisc (net/sched/sch_api.c:2352)
  tc_dump_tclass_root (net/sched/sch_api.c:2370)
  tc_dump_tclass (net/sched/sch_api.c:2431)
  rtnl_dumpit (net/core/rtnetlink.c:6864)
  netlink_dump (net/netlink/af_netlink.c:2325)
  rtnetlink_rcv_msg (net/core/rtnetlink.c:6959)
  netlink_rcv_skb (net/netlink/af_netlink.c:2550)
  </TASK>

Fix this by substituting &noop_qdisc when new is NULL in
taprio_graft(), a common pattern used by other qdiscs (e.g.,
multiq_graft()) to ensure the q->qdiscs[] slots are never NULL.
This makes control-plane dump paths safe without requiring individual
NULL checks.

Since the data-plane paths (taprio_enqueue and taprio_dequeue_from_txq)
previously had explicit NULL guards that would drop/skip the packet
cleanly, update those checks to test for &noop_qdisc instead. Without
this, packets would reach taprio_enqueue_one() which increments the root
qdisc's qlen and backlog before calling the child's enqueue; noop_qdisc
drops the packet but those counters are never rolled back, permanently
inflating the root qdisc's statistics.

After this change *old can be a valid qdisc, NULL, or &noop_qdisc.
Only call qdisc_put(*old) in the first case to avoid decreasing
noop_qdisc's refcount, which was never increased.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-45845?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-45845?

Apply the vendor's patch.

## Is CVE-2026-45845 being exploited?

There is no known exploitation of CVE-2026-45845 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-2026-45845 and fix it if it is affected.

What it is: CVE-2026-45845 is a medium-severity vulnerability in Linux kernel, published on 27 May 2026. 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-2026-45845 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-2026-45845/ (Markdown: https://insights.sbomify.com/CVE-2026-45845/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45845
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45845
- OSV: https://osv.dev/vulnerability/CVE-2026-45845

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45845/
Summaries are generated and may contain mistakes; the official description above is the record.