# CVE-2026-42960: Possible cache poisoning via promiscuous records for the authority section

> Attackers can poison the DNS cache by injecting malicious authority records, potentially redirecting users to malicious sites.

- **Severity:** Medium 5.7 (`CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:H/E:P/U:Amber`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 May 2026
- **Updated:** 20 May 2026
- **Also known as:** ALPINE-CVE-2026-42960, AZL-87018, CLSA-2026-1779960466, CLSA-2026-1779961008, DEBIAN-CVE-2026-42960, ECHO-6546-2c8e-af78, GHSA-x7f7-rggg-4jvv, ROOT-OS-DEBIAN-11-CVE-2026-42960, ROOT-OS-DEBIAN-12-CVE-2026-42960, UBUNTU-CVE-2026-42960

## What is CVE-2026-42960?

CVE-2026-42960 is a medium-severity vulnerability in Nlnetlabs Unbound, published on 20 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

NLnet Labs Unbound up to and including version 1.25.0 is vulnerable to poisoning via promiscuous records for the authority section. Promiscuous RRSets that complement DNS replies in the authority section can be used to trick Unbound to cache such records. If an adversary is able to attach such records in a reply (i.e., spoofed packet, fragmentation attack) he would be able to poison Unbound's cache. A malicious actor can exploit the possible poisonous effect by injecting RRSets other than NS that are also accompanied by address records in a reply, for example MX. This could be achieved by trying to spoof a reply packet or fragmentation attacks. Unbound would then accept the relative address records in the additional section and cache them if the authority RRSet has enough trust at this point, i.e., in-zone data for the delegation point. Unbound 1.25.1 contains a patch with a fix that disregards address records from the additional section if they are not explicitly relevant only to authority NS records, mitigating the possible poison effect. This is a complement fix to CVE-2025-11411.

Weakness: CWE-349 (Acceptance of Extraneous Untrusted Data With Trusted Data)

## Which versions are affected by CVE-2026-42960?

It affects 1 product.


Products: Nlnetlabs Unbound.

## How do I fix CVE-2026-42960?

Apply the vendor's patch.

## Is CVE-2026-42960 being exploited?

There is no known exploitation of CVE-2026-42960 in the wild and no public exploit code.

## Other vulnerabilities in Nlnetlabs Unbound

- [CVE-2026-81642](https://insights.sbomify.com/CVE-2026-81642/): Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY (critical 9.1)
- [CVE-2026-33278](https://insights.sbomify.com/CVE-2026-33278/): Possible arbitrary code execution during DNSSEC validation (critical 9.1)
- [CVE-2026-42944](https://insights.sbomify.com/CVE-2026-42944/): Heap overflow with multiple NSID, COOKIE, PADDING EDNS options (high 8.7)
- [CVE-2026-42959](https://insights.sbomify.com/CVE-2026-42959/): Crash during DNSSEC validation of malicious content (high 8.7)
- [CVE-2026-82717](https://insights.sbomify.com/CVE-2026-82717/): CNAME synthesis could lead to heap corruption (high 8.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42960 and fix it if it is affected.

What it is: CVE-2026-42960 is a medium-severity vulnerability in Nlnetlabs Unbound, published on 20 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-42960 in the wild and no public exploit code.

Affected product: Nlnetlabs Unbound. 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-2026-42960/ (Markdown: https://insights.sbomify.com/CVE-2026-42960/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42960
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42960
- OSV: https://osv.dev/vulnerability/CVE-2026-42960

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42960/
Summaries are generated and may contain mistakes; the official description above is the record.