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CVE-2026-5188— Integer underflow in X.509 SAN parsing in wolfSSL

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.

wolfSSL（CyaSSL）是美国wolfSSL公司的一个针对嵌入式系统开发人员使用的小的、可移植的嵌入式SSL编程库。 wolfSSL存在安全漏洞，该漏洞源于解析X.509证书时存在整数下溢问题，可能导致证书数据处理不当。

AI Predicted 4.3 Difficulty: Moderate EPSS 0.22% · P11

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-5188

Vulnerability Information
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Vulnerability Title
Integer underflow in X.509 SAN parsing in wolfSSL
Source: CVE Program / CVE List V5
Vulnerability Description
An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN) extension of X.509 certificates. A malformed certificate can specify an entry length larger than the enclosing sequence, causing the internal length counter to wrap during parsing. This results in incorrect handling of certificate data. The issue is limited to configurations using the original ASN.1 parsing implementation which is off by default.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
整数下溢(超界折返)
Source: CVE Program / CVE List V5
Vulnerability Title
wolfSSL 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
wolfSSL（CyaSSL）是美国wolfSSL公司的一个针对嵌入式系统开发人员使用的小的、可移植的嵌入式SSL编程库。 wolfSSL存在安全漏洞，该漏洞源于解析X.509证书时存在整数下溢问题，可能导致证书数据处理不当。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
wolfSSL wolfSSL 0 ~ 5.9.0 -

II. Public POCs for CVE-2026-5188

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III. Intelligence Information for CVE-2026-5188

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Patches & Fixes for CVE-2026-5188 (1)

Same Patch Batch · wolfSSL · 2026-04-10 · 6 CVEs total

CVE-2026-5479 wolfSSL EVP ChaCha20-Poly1305 AEAD authentication tag
CVE-2026-5466 wc_VerifyEccsiHash missing sanity check
CVE-2026-5501 Improper Certificate Signature Verification in X.509 Chain Validation Allows Forged Leaf C
CVE-2026-5477 Prefix-substitution forgery via integer overflow in wolfCrypt CMAC
CVE-2026-5500 Improper Validation of AES-GCM Authentication Tag Length in PKCS#7 Envelope Allows Authent

IV. Related Vulnerabilities

Same product: wolfSSL
Same vendor: wolfSSL
Same weakness: CWE-191

V. Comments for CVE-2026-5188

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