# CVE-2026-23270: net/sched: Only allow act_ct to bind to clsact/ingress qdiscs and shared blocks

> A use-after-free vulnerability in the Linux kernel's net/sched subsystem allows attackers to execute arbitrary code or escalate privileges via crafted network packets.

- **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:** 18 Mar 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-23270, DEBIAN-CVE-2026-23270, GHSA-62jp-jvc3-7hh9, ROOT-OS-DEBIAN-12-CVE-2026-23270, ROOT-OS-DEBIAN-13-CVE-2026-23270, ROOT-OS-UBUNTU-2204-CVE-2026-23270, ROOT-OS-UBUNTU-2404-CVE-2026-23270, UBUNTU-CVE-2026-23270

## What is CVE-2026-23270?

CVE-2026-23270 is a high-severity use after free vulnerability in Linux kernel, published on 18 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:

net/sched: Only allow act_ct to bind to clsact/ingress qdiscs and shared blocks

As Paolo said earlier [1]:

"Since the blamed commit below, classify can return TC_ACT_CONSUMED while
the current skb being held by the defragmentation engine. As reported by
GangMin Kim, if such packet is that may cause a UaF when the defrag engine
later on tries to tuch again such packet."

act_ct was never meant to be used in the egress path, however some users
are attaching it to egress today [2]. Attempting to reach a middle
ground, we noticed that, while most qdiscs are not handling
TC_ACT_CONSUMED, clsact/ingress qdiscs are. With that in mind, we
address the issue by only allowing act_ct to bind to clsact/ingress
qdiscs and shared blocks. That way it's still possible to attach act_ct to
egress (albeit only with clsact).

[1] https://lore.kernel.org/netdev/674b8cbfc385c6f37fb29a1de08d8fe5c2b0fbee.1771321118.git.pabeni@redhat.com/
[2] https://lore.kernel.org/netdev/cc6bfb4a-4a2b-42d8-b9ce-7ef6644fb22b@ovn.org/

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-23270?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23270?

Apply the vendor's patch.

## Is CVE-2026-23270 being exploited?

There is no known exploitation of CVE-2026-23270 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-2026-23270 and fix it if it is affected.

What it is: CVE-2026-23270 is a high-severity use after free vulnerability in Linux kernel, published on 18 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-2026-23270 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-2026-23270/ (Markdown: https://insights.sbomify.com/CVE-2026-23270/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23270
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23270
- OSV: https://osv.dev/vulnerability/CVE-2026-23270

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23270/
Summaries are generated and may contain mistakes; the official description above is the record.