Stack buffer overflow in PKCS7 SignedData encoding with custom signed attributes

A stack buffer overflow vulnerability exists in wolfSSL's PKCS7 SignedData encoding functionality. In wc_PKCS7_BuildSignedAttributes(), when adding custom signed attributes, the code passes an incorrect capacity value (esd->signedAttribsCount) to EncodeAttributes() instead of the remaining available space in the fixed-size signedAttribs[7] array. When an application sets pkcs7->signedAttribsSz to a value greater than MAX_SIGNED_ATTRIBS_SZ (default 7) minus the number of default attributes already added, EncodeAttributes() writes beyond the array bounds, causing stack memory corruption. In WOLFSSL_SMALL_STACK builds, this becomes heap corruption. Exploitation requires an application that allows untrusted input to control the signedAttribs array size when calling wc_PKCS7_EncodeSignedData() or related signing functions.

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栈缓冲区溢出

wolfSSL 安全漏洞

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PKCS7 SignedData编码功能存在栈缓冲区溢出，当应用程序设置pkcs7->signedAttribsSz值过大时，可能导致栈内存损坏，在WOLFSSL_SMALL_STACK构建中则导致堆损坏。

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