# CVE-2023-4236: named may terminate unexpectedly under high DNS-over-TLS query load

> Attackers can cause the BIND DNS server to crash by sending high volumes of DNS-over-TLS queries, requiring DoT to be enabled.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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:** 20 Sep 2023
- **Updated:** 13 Feb 2025
- **Also known as:** ALPINE-CVE-2023-4236, BELL-CVE-2023-4236, DEBIAN-CVE-2023-4236, GHSA-jhh4-vhhc-xpjq, UBUNTU-CVE-2023-4236

## What is CVE-2023-4236?

CVE-2023-4236 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 20 Sep 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A flaw in the networking code handling DNS-over-TLS queries may cause `named` to terminate unexpectedly due to an assertion failure. This happens when internal data structures are incorrectly reused under significant DNS-over-TLS query load.
This issue affects BIND 9 versions 9.18.0 through 9.18.18 and 9.18.11-S1 through 9.18.18-S1.

Weakness: CWE-617 (Reachable Assertion)

## Which versions are affected by CVE-2023-4236?

It affects 8 products.


Products: Debian Debian Linux, Fedoraproject Fedora, Isc Bind, Netapp H300s Firmware, Netapp H410c Firmware, Netapp H410s Firmware, Netapp H500s Firmware, Netapp H700s Firmware.

## How do I fix CVE-2023-4236?

Upgrade to a fixed version.

## Is CVE-2023-4236 being exploited?

There is no known exploitation of CVE-2023-4236 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-4236 and fix it if it is affected.

What it is: CVE-2023-4236 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 20 Sep 2023. 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-2023-4236 in the wild and no public exploit code.

Affected product: Debian Debian 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-2023-4236/ (Markdown: https://insights.sbomify.com/CVE-2023-4236/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-4236
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-4236
- OSV: https://osv.dev/vulnerability/CVE-2023-4236

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-4236/
Summaries are generated and may contain mistakes; the official description above is the record.