CVE-2026-3833: A flaw was found in gnutls

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MEDIUM 6.5REMOTEWATCHLISTMITIGATEMITIGATEDOWNGRADE

CVE-2026-3833 is a medium-severity flaw (CVSS 6.5) affecting gnutls, hardened images, openshift container platform. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 reject

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action
On your watchlist

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 53%)
CISA exploited list	No
Weakness	CWE-178
Published	2026-04-30
Last modified	2026-10-26

Publisher (CNA): Red Hat, Inc. · Vendor: gnu · redhat

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-30 18:16 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

gnu gnutls MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy gnutls || rpm -q gnutls || gnutls --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

redhat hardened images MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy hardened-images || rpm -q hardened-images || hardened-images --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

redhat openshift container platform DOWNGRADE

Affected: 4.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.0

1. Check installed version

apt-cache policy openshift-container-platform || rpm -q openshift-container-platform || openshift-container-platform --version

2. No fixed release: DOWNGRADE to a release before 4.0 (Debian / Ubuntu)

apt-cache madison openshift-container-platform sudo apt install openshift-container-platform=<VERSION_BEFORE_4.0> sudo apt-mark hold openshift-container-platform

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list openshift-container-platform sudo dnf downgrade openshift-container-platform-<VERSION_BEFORE_4.0> sudo dnf versionlock add openshift-container-platform

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

redhat enterprise linux MITIGATE

Affected: 6.0 · 7.0 · 8.0 · 9.0 · 10.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 6.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Advisories and coverage

Official advisories

CERT/CC Vulnerability Notes: VU#948176: Multiple TLS libraries can bypass delegation enforcement 2026-10-14
CERT/CC Vulnerability Notes: VU#573195: Go, OpenSSL, Apple, LibreSSL, pyca, wolfSSL Name-Constraint Inconsistency in RFC 5280 Implementation 2026-10-13
AlmaLinux Errata: [ALSA-2026:20612] Important: gnutls security update 2026-07-02

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-3833?

gnutls: mitigate or apply the listed mitigation; hardened images: mitigate or apply the listed mitigation; openshift container platform: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-3833 being exploited?

CVE-2026-3833 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-3833 affect?

CVE-2026-3833 affects gnutls, hardened images, openshift container platform. Severity is medium (CVSS 6.5). 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 `permitt

How urgent is CVE-2026-3833?

Priority 49/100. Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Red Hat OpenShift vulnerabilities · GnuTLS vulnerabilities

Related CVEs

CVE-2026-33845 HIGH 7.5 MITIGATE DOWNGRADE A flaw in GnuTLS DTLS handshake parsing allows malformed fragments with zero length and non-zero offset, leadi
CVE-2026-42010 HIGH 7.1 MITIGATE MITIGATE A flaw was found in gnutls
CVE-2026-1584 HIGH 7.5 MITIGATE MITIGATE A flaw was found in gnutls
CVE-2026-3832 LOW 3.7 MITIGATE MITIGATE A flaw was found in gnutls
CVE-2026-42009 HIGH 7.5 MITIGATE MITIGATE A flaw was found in gnutls

References

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