# CVE-2026-27853: Out-of-bounds write when rewriting large DNS packets

> Attackers can cause a denial of service in DNSdist by triggering an out-of-bounds write via crafted DNS responses processed by custom Lua scripts.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/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:** 31 Mar 2026
- **Updated:** 31 Mar 2026
- **Also known as:** DEBIAN-CVE-2026-27853, GHSA-w68q-j3pw-29rg, UBUNTU-CVE-2026-27853

## What is CVE-2026-27853?

CVE-2026-27853 is a medium-severity memory corruption vulnerability in PowerDNS DNSdist, published on 31 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An attacker might be able to trigger an out-of-bounds write by sending crafted DNS responses to a DNSdist using the DNSQuestion:changeName or DNSResponse:changeName methods in custom Lua code. In some cases the rewritten packet might become larger than the initial response and even exceed 65535 bytes, potentially leading to a crash resulting in denial of service.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-27853?

It affects 1 product.


Products: Powerdns Dnsdist.

## How do I fix CVE-2026-27853?

Apply the vendor's patch.

## Is CVE-2026-27853 being exploited?

There is no known exploitation of CVE-2026-27853 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-2026-33602](https://insights.sbomify.com/CVE-2026-33602/): Off-by-one access when processing crafted UDP responses (medium 6.5)
- [CVE-2026-24029](https://insights.sbomify.com/CVE-2026-24029/): DNS over HTTPS ACL bypass (medium 6.5)
- [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-2026-27853 and fix it if it is affected.

What it is: CVE-2026-27853 is a medium-severity memory corruption vulnerability in PowerDNS DNSdist, published on 31 Mar 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-2026-27853 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-2026-27853/ (Markdown: https://insights.sbomify.com/CVE-2026-27853/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27853
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27853
- OSV: https://osv.dev/vulnerability/CVE-2026-27853

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27853/
Summaries are generated and may contain mistakes; the official description above is the record.