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CVE-2026-5500— Improper Validation of AES-GCM Authentication Tag Length in PKCS#7 Envelope Allows Authentication Bypass

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（CyaSSL）存在安全漏洞，该漏洞源于wc_PKCS7_DecodeAuthEnvelopedData函数未正确清理接收的AES-GCM身份验证标签长度且缺少下限检查，可能导致中间人攻击者将mac字段从16字节截断至1字节，从而降低标签检查强度。

AI Predicted 8.1 Difficulty: Moderate EPSS 0.38% · P30

Possible ATT&CK Techniques 1 AI

T1557 · Adversary-in-the-Middle
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I. Basic Information for CVE-2026-5500

Vulnerability Information
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Vulnerability Title
Improper Validation of AES-GCM Authentication Tag Length in PKCS#7 Envelope Allows Authentication Bypass
Source: CVE Program / CVE List V5
Vulnerability Description
wolfSSL's wc_PKCS7_DecodeAuthEnvelopedData() does not properly sanitize the AES-GCM authentication tag length received and has no lower bounds check. A man-in-the-middle can therefore truncate the mac field from 16 bytes to 1 byte, reducing the tag check from 2⁻¹²⁸ to 2⁻⁸.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
wolfSSL（CyaSSL） 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（CyaSSL）存在安全漏洞，该漏洞源于wc_PKCS7_DecodeAuthEnvelopedData函数未正确清理接收的AES-GCM身份验证标签长度且缺少下限检查，可能导致中间人攻击者将mac字段从16字节截断至1字节，从而降低标签检查强度。
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-2026-5500

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III. Intelligence Information for CVE-2026-5500

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Patches & Fixes for CVE-2026-5500 (1)

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

CVE-2026-5479 wolfSSL EVP ChaCha20-Poly1305 AEAD authentication tag
CVE-2026-5188 Integer underflow in X.509 SAN parsing in wolfSSL
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

IV. Related Vulnerabilities

Same product: wolfSSL
Same vendor: wolfSSL
Same weakness: CWE-20

V. Comments for CVE-2026-5500

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