# CVE-2026-33602: Off-by-one access when processing crafted UDP responses

> A rogue backend can trigger an out-of-bounds write via crafted UDP responses, causing a denial of service in PowerDNS DNSdist.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/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 Apr 2026
- **Updated:** 22 Apr 2026
- **Also known as:** DEBIAN-CVE-2026-33602, GHSA-3hg3-qp28-5p96, UBUNTU-CVE-2026-33602

## What is CVE-2026-33602?

CVE-2026-33602 is a medium-severity memory corruption vulnerability in PowerDNS DNSdist, published on 22 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A rogue backend can send a crafted UDP response with a query ID off by one related to the maximum configured value, triggering an out-of-bounds write leading to a denial of service.

Weakness: CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-33602?

It affects 1 product.


Products: Powerdns Dnsdist.

## How do I fix CVE-2026-33602?

Apply the vendor's patch.

## Is CVE-2026-33602 being exploited?

There is no known exploitation of CVE-2026-33602 in the wild and no public exploit code.

## Other vulnerabilities in PowerDNS DNSdist

- [CVE-2017-7557](https://insights.sbomify.com/CVE-2017-7557/): Cross-site request forgery in dnsdist (high 8.8)
- [CVE-2026-33593](https://insights.sbomify.com/CVE-2026-33593/): Denial of service via crafted DNSCrypt query (high 7.5)
- [CVE-2026-24029](https://insights.sbomify.com/CVE-2026-24029/): DNS over HTTPS ACL bypass (medium 6.5)
- [CVE-2026-27853](https://insights.sbomify.com/CVE-2026-27853/): Out-of-bounds write when rewriting large DNS packets (medium 5.9)
- [CVE-2018-14663](https://insights.sbomify.com/CVE-2018-14663/): Other in dnsdist (medium 5.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-33602 and fix it if it is affected.

What it is: CVE-2026-33602 is a medium-severity memory corruption vulnerability in PowerDNS DNSdist, published on 22 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-2026-33602 in the wild and no public exploit code.

Affected product: PowerDNS DNSdist. 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-2026-33602/ (Markdown: https://insights.sbomify.com/CVE-2026-33602/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33602
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33602
- OSV: https://osv.dev/vulnerability/CVE-2026-33602

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-33602/
Summaries are generated and may contain mistakes; the official description above is the record.