Description
Botan is a C++ cryptography library. Prior to version 3.11.0, during processing of an X.509 certificate path using name constraints which restrict the set of allowable DNS names, if no subject alternative name is defined in the end-entity certificate Botan would check that the CN was allowed by the DNS name constraints, even though this check is technically not required by RFC 5280. However this check failed to account for the possibility of a mixed-case CN. Thus a certificate with CN=Sub.EVIL.COM and no subject alternative name would bypasses an excludedSubtrees constraint for evil.com because the comparison is case-sensitive. This issue has been patched in version 3.11.0.
Published: 2026-03-30
Score: 5.9 Medium
EPSS: < 1% Very Low
KEV: No
Impact: Bypasses name constraints in X.509 certificate validation
Action: Immediate Patch
AI Analysis

Impact

A flaw in Botan's handling of name constraints allows a certificate with a mixed‑case Common Name and no Subject Alternative Name to bypass DNS excludedSubtrees restrictions. The library performs a case‑sensitive comparison during path validation, which is incorrect per RFC 5280. Consequently, an attacker can issue a certificate that appears valid to the library while violating the intended name constraint policy, enabling potential impersonation or fraud.

Affected Systems

This issue affects the Randombit Botan C++ cryptography library in all releases prior to version 3.11.0. Software that incorporates Botan without upgrading may be vulnerable if it validates X.509 certificates with name constraints.

Risk and Exploitability

The vulnerability carries a CVSS score of 5.9, indicating moderate severity. EPSS data is not available, and it is not listed in the CISA KEV catalog. The attack vector is inferred to be remote: an adversary can simply submit a specially crafted certificate to an application that performs certificate path validation using Botan. Because the flaw lies in the library's internal logic, no additional conditions are required beyond the presence of name constraints and a CN with mixed case.

Generated by OpenCVE AI on March 31, 2026 at 05:39 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Upgrade to Botan version 3.11.0 or later
  • If immediate upgrade is not possible, modify or supplement validation logic to enforce case‑insensitive CN checks or require a Subject Alternative Name
  • Maintain up‑to‑date dependencies and monitor for related advisories

Generated by OpenCVE AI on March 31, 2026 at 05:39 UTC.

Tracking

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Advisories

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History

Wed, 01 Apr 2026 02:15:00 +0000

Type Values Removed Values Added
First Time appeared Randombit
Randombit botan
Vendors & Products Randombit
Randombit botan

Tue, 31 Mar 2026 19:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Tue, 31 Mar 2026 03:00:00 +0000

Type Values Removed Values Added
Description Botan is a C++ cryptography library. Prior to version 3.11.0, during processing of an X.509 certificate path using name constraints which restrict the set of allowable DNS names, if no subject alternative name is defined in the end-entity certificate Botan would check that the CN was allowed by the DNS name constraints, even though this check is technically not required by RFC 5280. However this check failed to account for the possibility of a mixed-case CN. Thus a certificate with CN=Sub.EVIL.COM and no subject alternative name would bypasses an excludedSubtrees constraint for evil.com because the comparison is case-sensitive. This issue has been patched in version 3.11.0.
Title Botan: Case-Insensitive CN Values Bypass DNS excludedSubtrees Name Constraints (RFC 5280 Violation)
Weaknesses CWE-295
References
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N'}

Subscriptions

Randombit Botan
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-03-31T18:53:35.754Z

Reserved: 2026-03-16T21:03:44.421Z

Link: CVE-2026-32884

cve-icon Vulnrichment

Updated: 2026-03-31T18:50:35.503Z

cve-icon NVD

Status : Received

Published: 2026-03-30T21:17:10.093

Modified: 2026-03-30T21:17:10.093

Link: CVE-2026-32884

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-03-31T20:40:05Z

Weaknesses