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CVE-2026-89134— Subject CN name-constraint check bypassed when non-DNS SAN present

Quick assessment

Affected
wolfSSL wolfSSL
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在存在非 dNSName 类型 SAN（例如 registeredID 或 iPAddress）但没有 dNSName 类型 SAN 的证书场景中，系统绕过了对主体通用名（Subject CN）中 dNSName 的名称约束检查。CN 作为 DNS 名称的后备机制原本仅在条件 成立时启用，而非基于“是否存在 dNSName SAN”的判断，从而导致域外范围的 CN 被错误接受。此漏洞源于 CVE-2026-6731 的不完整修复措施，该问题在 wolfSSL 5.9.2 版本中被引入。

CVSS 6.3 · Medium EPSS 0.22% · P11

Possible ATT&CK Techniques 1 AI

T1557 · Adversary-in-the-Middle
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I. Basic Information for CVE-2026-89134

Vulnerability Information
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Vulnerability Title
Subject CN name-constraint check bypassed when non-DNS SAN present
Source: CVE Program / CVE List V5
Vulnerability Description
A certificate with no dNSName SAN but another SAN type present (e.g. registeredID or iPAddress) bypassed the Subject CN dNSName name-constraint check. The CN-as-DNS fallback was gated on cert->subjectCN != NULL && cert->altNames == NULL && !cert->isCA instead of "no dNSName SAN", so an out-of-scope CN was accepted. This incomplete fix from CVE-2026-6731, leading to the name-constraint check issue, was introduced in wolfSSL version 5.9.2.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
证书验证不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
wolfSSL wolfSSL 5.9.2 -

II. Public POCs for CVE-2026-89134

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III. Intelligence Information for CVE-2026-89134

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Other References for CVE-2026-89134 (1)

Same Patch Batch · wolfSSL · 2026-09-27 · 11 CVEs total

CVE-2026-93302 8.3 HIGH Trusted peer certificate match ignores public key, allowing forged CA clones
CVE-2026-89136 8.3 HIGH Client accepts unsolicited RawPublicKey server certificate type
CVE-2026-89102 8.3 HIGH OCSP stapling v2 multi accepts non-CA chain certificates as issuers
CVE-2026-93304 6.3 MEDIUM (D)TLS 1.2 client accepts early ChangeCipherSpec before ClientKeyExchange
CVE-2026-89133 6.3 MEDIUM NameConstraints not enforced across unconstrained intermediate CA
CVE-2026-89135 6.3 MEDIUM Failed X509_verify_cert leaves unverified CA in shared CertManager
CVE-2026-15442 2.3 LOW Heap use-after-free on read during bidirectional (D)TLS shutdown
CVE-2026-94418 2.3 LOW Signature failure masked by date error under WOLFSSL_SMALL_CERT_VERIFY
CVE-2026-94419 2.3 LOW Client session cache reference poisoning allows resumption with wrong server
CVE-2026-94417 2.3 LOW CRL check skipped when OCSP enabled and certificate has no OCSP URL

IV. Related Vulnerabilities

Same product: wolfSSL
Same vendor: wolfSSL
Same weakness: CWE-295

V. Comments for CVE-2026-89134

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