# CVE-2026-23456: netfilter: nf_conntrack_h323: fix OOB read in decode_int() CONS case

> A malformed H.323 packet can trigger an out-of-bounds read in the Linux kernel's netfilter module, potentially leaking memory or causing a crash.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 3 Apr 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-23456, DEBIAN-CVE-2026-23456, GHSA-qgh9-fcm6-v6pg, ROOT-OS-DEBIAN-11-CVE-2026-23456, ROOT-OS-DEBIAN-12-CVE-2026-23456, ROOT-OS-DEBIAN-13-CVE-2026-23456, ROOT-OS-UBUNTU-2204-CVE-2026-23456, ROOT-OS-UBUNTU-2404-CVE-2026-23456, UBUNTU-CVE-2026-23456

## What is CVE-2026-23456?

CVE-2026-23456 is a high-severity memory corruption vulnerability in Linux kernel, published on 3 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_conntrack_h323: fix OOB read in decode_int() CONS case

In decode_int(), the CONS case calls get_bits(bs, 2) to read a length
value, then calls get_uint(bs, len) without checking that len bytes
remain in the buffer. The existing boundary check only validates the
2 bits for get_bits(), not the subsequent 1-4 bytes that get_uint()
reads. This allows a malformed H.323/RAS packet to cause a 1-4 byte
slab-out-of-bounds read.

Add a boundary check for len bytes after get_bits() and before
get_uint().

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-23456?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23456?

Apply the vendor's patch.

## Is CVE-2026-23456 being exploited?

There is no known exploitation of CVE-2026-23456 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-2026-23456 and fix it if it is affected.

What it is: CVE-2026-23456 is a high-severity memory corruption vulnerability in Linux kernel, published on 3 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-23456 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-2026-23456/ (Markdown: https://insights.sbomify.com/CVE-2026-23456/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23456
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23456
- OSV: https://osv.dev/vulnerability/CVE-2026-23456

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23456/
Summaries are generated and may contain mistakes; the official description above is the record.