# CVE-2026-40012: Information about ECS zero scoped answers might leak to clients that use a specific ECS

> Attackers can leak ECS zero scoped answers from the packet cache in PowerDNS Recursor when ECS is enabled.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Jun 2026
- **Updated:** 25 Jun 2026
- **Also known as:** DEBIAN-CVE-2026-40012, GHSA-fmvv-f47m-6c7p, UBUNTU-CVE-2026-40012

## What is CVE-2026-40012?

CVE-2026-40012 is a medium-severity vulnerability in PowerDNS Recursor, published on 25 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

ECS zero scoped answers are stored in the packet cache while they should not. This impacts only configurations that have ECS enabled;

Weakness: CWE-524 (Use of Cache Containing Sensitive Information)

## Which versions are affected by CVE-2026-40012?


## How do I fix CVE-2026-40012?

Apply the vendor's patch.

## Is CVE-2026-40012 being exploited?

There is no known exploitation of CVE-2026-40012 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40012 and fix it if it is affected.

What it is: CVE-2026-40012 is a medium-severity vulnerability in PowerDNS Recursor, published on 25 Jun 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-2026-40012 in the wild and no public exploit code.

Affected product: PowerDNS Recursor. 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-2026-40012/ (Markdown: https://insights.sbomify.com/CVE-2026-40012/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40012
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40012
- OSV: https://osv.dev/vulnerability/CVE-2026-40012

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40012/
Summaries are generated and may contain mistakes; the official description above is the record.