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CVE-2026-3547— wolfSSL: out-of-bounds read (DoS) in ALPN parsing due to incomplete validation

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） 5.8.4及之前版本存在安全漏洞，该漏洞源于ALPN解析存在越界读取，且验证不完整，可能导致特制的ALPN协议列表触发越界读取，造成进程崩溃。

CVSS 7.5 · High EPSS 0.44% · P36

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service
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I. Basic Information for CVE-2026-3547

Vulnerability Information
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Vulnerability Title
wolfSSL: out-of-bounds read (DoS) in ALPN parsing due to incomplete validation
Source: CVE Program / CVE List V5
Vulnerability Description
Out-of-bounds read in ALPN parsing due to incomplete validation. wolfSSL 5.8.4 and earlier contained an out-of-bounds read in ALPN handling when built with ALPN enabled (HAVE_ALPN / --enable-alpn). A crafted ALPN protocol list could trigger an out-of-bounds read, leading to a potential process crash (denial of service). Note that ALPN is disabled by default, but is enabled for these 3rd party compatibility features: enable-apachehttpd, enable-bind, enable-curl, enable-haproxy, enable-hitch, enable-lighty, enable-jni, enable-nginx, enable-quic.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存读
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及之前版本存在安全漏洞，该漏洞源于ALPN解析存在越界读取，且验证不完整，可能导致特制的ALPN协议列表触发越界读取，造成进程崩溃。
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 wolfSSL 0 ~ 5.9.0 -

II. Public POCs for CVE-2026-3547

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III. Intelligence Information for CVE-2026-3547

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Patches & Fixes for CVE-2026-3547 (1)

Same Patch Batch · wolfSSL · 2026-03-19 · 11 CVEs total

CVE-2026-0819 Stack buffer overflow in PKCS7 SignedData encoding with custom signed attributes
CVE-2026-1005 Integer underflow leads to out-of-bounds access in sniffer AES-GCM/CCM/ARIA-GCM decrypt pa
CVE-2026-2646 Heap buffer overflow in session parsing with wolfSSL_d2i_SSL_SESSION() function
CVE-2026-2645 Acceptance of CertificateVerify Message before ClientKeyExchange in TLS 1.2
CVE-2026-3548 Buffer overflow in CRL number parsing in wolfSSL
CVE-2026-3579 Non-constant time multiplication subroutine __muldi3 on RISC-V RV32I
CVE-2026-3580 Compiler-induced timing leak in sp_256_get_entry_256_9 on RISC-V
CVE-2026-4395 Heap-based buffer overflow in wc_ecc_import_x963_ex KCAPI path
CVE-2026-3230 Improper key_share validation in TLS 1.3 HelloRetryRequest
CVE-2026-4159 wc_PKCS7_DecodeEnvelopedData 1 byte out-of-bounds read

IV. Related Vulnerabilities

Same product: wolfSSL
Same vendor: wolfSSL
Same weakness: CWE-125

V. Comments for CVE-2026-3547

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