# CVE-2026-13204: Unexpected exit in certain situations with NSEC and NSEC3 both present

> An attacker can cause a denial of service in BIND by triggering an assertion failure when validating domains with mixed NSEC and NSEC3 records.

- **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:** 22 Jul 2026
- **Updated:** 22 Jul 2026
- **Also known as:** ALPINE-CVE-2026-13204, AZL-93117, BELL-CVE-2026-13204, CLSA-2026-1785267075, CLSA-2026-1785309449, CLSA-2026-1785309455, DEBIAN-CVE-2026-13204, ECHO-fcc4-5d8a-b7af, GHSA-89q8-qc36-7m58, MGASA-2026-0399, MINI-9m48-xqx8-fhpg, MINI-crm8-pqm4-mq49, MINI-mfc7-32fg-cfrp, UBUNTU-CVE-2026-13204, USN-8696-1

## What is CVE-2026-13204?

CVE-2026-13204 is a high-severity denial of service vulnerability in ISC BIND 9, published on 22 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

If a provably insecure domain is covered by both an NSEC and NSEC3 record at the parent, and there exist an RRSIG for only one of these types, then BIND may exit unexpectedly with an assertion while validating this proof.
This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.

Weakness: CWE-617 (Reachable Assertion)

## Which versions are affected by CVE-2026-13204?


## How do I fix CVE-2026-13204?

Apply the vendor's patch.

## Is CVE-2026-13204 being exploited?

There is no known exploitation of CVE-2026-13204 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-13204 and fix it if it is affected.

What it is: CVE-2026-13204 is a high-severity denial of service vulnerability in ISC BIND 9, published on 22 Jul 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-2026-13204 in the wild and no public exploit code.

Affected product: ISC BIND 9. 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-2026-13204/ (Markdown: https://insights.sbomify.com/CVE-2026-13204/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-13204
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-13204
- OSV: https://osv.dev/vulnerability/CVE-2026-13204

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-13204/
Summaries are generated and may contain mistakes; the official description above is the record.