CVE-2026-3849— Buffer Overflow in HPKE via Oversized ECH Config
Quick assessment
Affected
wolfSSL Inc. 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）5.8.4版本存在安全漏洞，该漏洞源于ECH支持中存在栈缓冲区溢出，恶意特制的ECH配置可能导致客户端栈缓冲区溢出，从而可能引发远程代码执行和客户端程序崩溃。
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I. Basic Information for CVE-2026-3849
Vulnerability Information
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Vulnerability Title
Buffer Overflow in HPKE via Oversized ECH Config
Source: CVE Program / CVE List V5
Vulnerability Description
Stack Buffer Overflow in wc_HpkeLabeledExtract via Oversized ECH Config. A vulnerability existed in wolfSSL 5.8.4 ECH (Encrypted Client Hello) support, where a maliciously crafted ECH config could cause a stack buffer overflow on the client side, leading to potential remote execution and client program crash. This could be exploited by a malicious TLS server supporting ECH. Note that ECH is off by default, and is only enabled with enable-ech.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/V:D/RE:M/U:Amber
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存写
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）5.8.4版本存在安全漏洞，该漏洞源于ECH支持中存在栈缓冲区溢出，恶意特制的ECH配置可能导致客户端栈缓冲区溢出，从而可能引发远程代码执行和客户端程序崩溃。
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 Inc. | wolfSSL | v5.6.0-stable ~ v5.8.4-stable | - |
|
II. Public POCs for CVE-2026-3849
| # | POC Description | Source Link | Shenlong Link |
|---|
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Patches & Fixes for CVE-2026-3849 (1)
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V. Comments for CVE-2026-3849
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