# CVE-2026-23274: netfilter: xt_IDLETIMER: reject rev0 reuse of ALARM timer labels

> A local attacker can cause a kernel panic by reusing an uninitialized timer label in netfilter IDLETIMER rules, requiring panic_on_warn enabled.

- **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:** 20 Mar 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-80201, BELL-CVE-2026-23274, DEBIAN-CVE-2026-23274, GHSA-3cwp-73f3-j7w3, ROOT-OS-DEBIAN-11-CVE-2026-23274, ROOT-OS-DEBIAN-12-CVE-2026-23274, ROOT-OS-DEBIAN-13-CVE-2026-23274, ROOT-OS-UBUNTU-2204-CVE-2026-23274, ROOT-OS-UBUNTU-2404-CVE-2026-23274, UBUNTU-CVE-2026-23274

## What is CVE-2026-23274?

CVE-2026-23274 is a high-severity vulnerability in Linux kernel, published on 20 Mar 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:

netfilter: xt_IDLETIMER: reject rev0 reuse of ALARM timer labels

IDLETIMER revision 0 rules reuse existing timers by label and always call
mod_timer() on timer->timer.

If the label was created first by revision 1 with XT_IDLETIMER_ALARM,
the object uses alarm timer semantics and timer->timer is never initialized.
Reusing that object from revision 0 causes mod_timer() on an uninitialized
timer_list, triggering debugobjects warnings and possible panic when
panic_on_warn=1.

Fix this by rejecting revision 0 rule insertion when an existing timer with
the same label is of ALARM type.

Weakness: CWE-758 (Reliance on Undefined, Unspecified, or Implementation-Defined Behavior)

## Which versions are affected by CVE-2026-23274?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23274?

Apply the vendor's patch.

## Is CVE-2026-23274 being exploited?

There is no known exploitation of CVE-2026-23274 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-2026-23274 and fix it if it is affected.

What it is: CVE-2026-23274 is a high-severity vulnerability in Linux kernel, published on 20 Mar 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-2026-23274 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-2026-23274/ (Markdown: https://insights.sbomify.com/CVE-2026-23274/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23274
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23274
- OSV: https://osv.dev/vulnerability/CVE-2026-23274

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23274/
Summaries are generated and may contain mistakes; the official description above is the record.