# CVE-2026-42012: Gnutls: gnutls: certificate validation bypass due to improper handling of uri and srv sans

> Remote attackers can bypass certificate validation by crafting specific SANs, enabling service spoofing and potential interception of sensitive data.

- **Severity:** High 7.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 26 May 2026
- **Updated:** 29 Oct 2026
- **Also known as:** ALPINE-CVE-2026-42012, AZL-89187, BELL-CVE-2026-42012, CLSA-2026-1789460699, DEBIAN-CVE-2026-42012, ECHO-abd3-5305-c7ca, GHSA-7hhj-8fwv-m5hc

## What is CVE-2026-42012?

CVE-2026-42012 is a high-severity vulnerability in Cert Manager support for Red Hat OpenShift release 1.17, published on 26 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

A flaw was found in gnutls. A remote attacker could exploit this vulnerability by presenting a specially crafted certificate that contains Uniform Resource Identifier (URI) or Service (SRV) Subject Alternative Names (SANs). This could cause the certificate validation process to incorrectly fall back to checking DNS hostnames against the Common Name (CN), potentially allowing the attacker to spoof legitimate services or intercept sensitive information.

Weakness: CWE-295 (Improper Certificate Validation)

## Which versions are affected by CVE-2026-42012?


## How do I fix CVE-2026-42012?

Apply the vendor's patch.

## Is CVE-2026-42012 being exploited?

There is no known exploitation of CVE-2026-42012 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42012 and fix it if it is affected.

What it is: CVE-2026-42012 is a high-severity vulnerability in Cert Manager support for Red Hat OpenShift release 1.17, published on 26 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-42012 in the wild and no public exploit code.

Affected product: Cert Manager support for Red Hat OpenShift release 1.17. 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-2026-42012/ (Markdown: https://insights.sbomify.com/CVE-2026-42012/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42012
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42012
- OSV: https://osv.dev/vulnerability/CVE-2026-42012

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-42012/
Summaries are generated and may contain mistakes; the official description above is the record.