# CVE-2026-98380: net/sched: reject IDR error pointers when deleting actions

> A race condition in the Linux kernel's traffic control subsystem allows a local attacker to trigger a null pointer dereference, causing a system crash.

- **Severity:** Not scored
- **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:** 9 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-106908, BELL-CVE-2026-98380, DEBIAN-CVE-2026-98380, GHSA-j546-37mc-3c35, UBUNTU-CVE-2026-98380

## What is CVE-2026-98380?

CVE-2026-98380 is a vulnerability in Linux, published on 9 Oct 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: reject IDR error pointers when deleting actions

tcf_action_delete() drops the reference held by its lookup before calling
tcf_idr_delete_index() with the saved action index.  An unlocked
classifier can remove that action and reserve the same IDR slot with
ERR_PTR(-EBUSY) in between.

tcf_idr_delete_index() only checks the lookup result for NULL.  It
therefore treats the reservation as a tc_action and dereferences
tcfa_bindcnt.  A hardware execution breakpoint was used to schedule the
interleaving without changing the kernel source.  KASAN reported this
decoded trace:

  BUG: KASAN: null-ptr-deref in tca_action_gd+0x5b9/0x1010
  Read of size 4 at addr 0000000000000010 by task poc/150
  Oops: general protection fault, probably for non-canonical address 0xdffffc0000000002
  RIP: tca_action_gd+0x5c0/0x1010:
    arch_atomic_read at arch/x86/include/asm/atomic.h:23
    raw_atomic_read at include/linux/atomic/atomic-arch-fallback.h:457
    atomic_read at include/linux/atomic/atomic-instrumented.h:33
    tcf_idr_delete_index at net/sched/act_api.c:766
    tcf_action_delete at net/sched/act_api.c:1859
    tcf_del_notify at net/sched/act_api.c:2014
    tca_action_gd at net/sched/act_api.c:2064
  R13: 0000000000000010 R15: fffffffffffffff0
  Kernel panic - not syncing: Fatal exception

R15 contains ERR_PTR(-EBUSY), and adding the tcfa_bindcnt offset produces
the address in R13.  With the guard applied, the same reproducer returned
-ENOENT without a KASAN report or panic.  Treat error pointers as absent
and return -ENOENT.

## Which versions are affected by CVE-2026-98380?


## How do I fix CVE-2026-98380?

Apply the vendor's patch.

## Is CVE-2026-98380 being exploited?

There is no known exploitation of CVE-2026-98380 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98380 and fix it if it is affected.

What it is: CVE-2026-98380 is a vulnerability in Linux, published on 9 Oct 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-2026-98380 in the wild and no public exploit code.

Affected product: 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-2026-98380/ (Markdown: https://insights.sbomify.com/CVE-2026-98380/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98380
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98380
- OSV: https://osv.dev/vulnerability/CVE-2026-98380

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98380/
Summaries are generated and may contain mistakes; the official description above is the record.