# CVE-2026-3833: Gnutls: gnutls: policy bypass due to case-sensitive nameconstraints comparison

> Attackers can bypass certificate name constraints by exploiting case-sensitive comparisons in GnuTLS, leading to unauthorized access or information disclosure.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/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:** 30 Apr 2026
- **Updated:** 14 Oct 2026
- **Also known as:** ALPINE-CVE-2026-3833, BELL-CVE-2026-3833, CLSA-2026-1778832314, CLSA-2026-1778835563, CLSA-2026-1778839424, CLSA-2026-1779107085, CLSA-2026-1779120347, CLSA-2026-1779120390, CLSA-2026-1779180457, CLSA-2026-1779355433, CLSA-2026-1779355613, CLSA-2026-1779827686, CLSA-2026-1779963183, DEBIAN-CVE-2026-3833, ECHO-eaab-3ed4-9bfd, GHSA-6rgh-57xm-37v8

## What is CVE-2026-3833?

CVE-2026-3833 is a medium-severity vulnerability in Gnu Gnutls, published on 30 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A flaw was found in gnutls. This vulnerability occurs because gnutls performs case-sensitive comparisons of `nameConstraints` labels, specifically for `dNSName` (DNS) or `rfc822Name` (email) constraints within `excludedSubtrees` or `permittedSubtrees`. A remote attacker can exploit this by crafting a leaf certificate with casing differences in the Subject Alternative Name (SAN), leading to a policy bypass where a certificate that should be rejected is instead accepted. This could result in unauthorized access or information disclosure.

Weakness: CWE-178 (Improper Handling of Case Sensitivity)

## Which versions are affected by CVE-2026-3833?

It affects 4 products.


Products: Gnu Gnutls, Redhat Enterprise Linux, Redhat Hardened Images, Redhat Openshift Container Platform.

## How do I fix CVE-2026-3833?

Apply the vendor's patch.

## Is CVE-2026-3833 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-3833 exists.

## Other vulnerabilities in Gnu Gnutls

- [CVE-2008-1948](https://insights.sbomify.com/CVE-2008-1948/): Memory corruption in n/a (critical 10.0)
- [CVE-2017-5334](https://insights.sbomify.com/CVE-2017-5334/): Use after free in n/a (critical 9.8)
- [CVE-2017-5336](https://insights.sbomify.com/CVE-2017-5336/): Memory corruption in n/a (critical 9.8)
- [CVE-2017-5337](https://insights.sbomify.com/CVE-2017-5337/): Memory corruption in n/a (critical 9.8)
- [CVE-2008-1949](https://insights.sbomify.com/CVE-2008-1949/): Null dereference in n/a (critical 9.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-3833 and fix it if it is affected.

What it is: CVE-2026-3833 is a medium-severity vulnerability in Gnu Gnutls, published on 30 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-3833 exists.

Affected product: Gnu Gnutls. 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-2026-3833/ (Markdown: https://insights.sbomify.com/CVE-2026-3833/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3833
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3833
- OSV: https://osv.dev/vulnerability/CVE-2026-3833

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-3833/
Summaries are generated and may contain mistakes; the official description above is the record.