CVE-2026-3833Network attack vectorHinoki check available

TLS impersonation via case-sensitive name constraints

Published Apr 30, 2026 · Updated Aug 26, 2026

Certificate-validation bypass in GnuTLS before 3.8.13 allows remote attackers to impersonate restricted TLS services using crafted certificates. lib/x509/name_constraints.c compares DNS labels and email-domain labels case-sensitively, accepting casing variants excluded by X.509 constraints. Exploitation requires a malicious or compromised constrained subordinate CA capable of issuing and presenting the crafted certificate.

CVSS severity6.5
Medium
EPSS probability0.56%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
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Summary

What happened

Certificate-validation bypass in GnuTLS before 3.8.13 allows remote attackers to impersonate restricted TLS services using crafted certificates. lib/x509/name_constraints.c compares DNS labels and email-domain labels case-sensitively, accepting casing variants excluded by X.509 constraints. Exploitation requires a malicious or compromised constrained subordinate CA capable of issuing and presenting the crafted certificate.

The record

CVE
CVE-2026-3833
Published
Apr 30, 2026
Updated
Aug 26, 2026
Vendor
389 Directory Server
Product
Red Hat Enterprise Linux 6
Classifications
CWE-178, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 30, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 26, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

389 Directory Server · Red Hat Enterprise Linux 6Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8.8 Update Services for SAP SolutionsAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 9.4 Update Services for SAP SolutionsAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 10Affected versions are unavailable in this record.
389 Directory Server · Red Hat Update Infrastructure 5Affected versions are unavailable in this record.
GnuTLS Project · GnuTLSversion=0 <3.8.13
389 Directory Server · Red Hat Enterprise Linux 9.2 Update Services for SAP SolutionsAffected versions are unavailable in this record.
389 Directory Server · Red Hat OpenShift Container Platform 4.19Affected versions are unavailable in this record.
389 Directory Server · Red Hat Hardened ImagesAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update SupportAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-OnAffected versions are unavailable in this record.
389 Directory Server · Red Hat Discovery 2Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 9Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-OnAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8.8 Telecommunications Update ServiceAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 7 Extended Lifecycle SupportAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 10.0 Extended Update SupportAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 9.6 Extended Update SupportAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update SupportAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8Affected versions are unavailable in this record.

Published CVSS scores

6.5CVE ProgramCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
6.5Red HatCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
7.4NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-178Improper Handling of Case Sensitivity
T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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