CVE-2026-39853— osslsigncode has a Stack Buffer Overflow via Unbounded Digest Copy During Signature Verification

osslsigncode has a Stack Buffer Overflow via Unbounded Digest Copy During Signature Verification

osslsigncode is a tool that implements Authenticode signing and timestamping. Prior to 2.12, A stack buffer overflow vulnerability exists in osslsigncode in several signature verification paths. During verification of a PKCS#7 signature, the code copies the digest value from a parsed SpcIndirectDataContent structure into a fixed-size stack buffer (mdbuf[EVP_MAX_MD_SIZE], 64 bytes) without validating that the source length fits within the destination buffer. This pattern is present in the verification handlers for PE, MSI, CAB, and script files. An attacker can craft a malicious signed file with an oversized digest field in SpcIndirectDataContent. When a user verifies such a file with osslsigncode verify, the unbounded memcpy can overflow the stack buffer and corrupt adjacent stack state. This vulnerability is fixed in 2.12.

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

栈缓冲区溢出

osslsigncode 缓冲区错误漏洞

osslsigncode是Michał Trojnara个人开发者的一个小型工具。实现了 Microsoft 工具 signtool.exe 的部分功能。 osslsigncode 2.12之前版本存在缓冲区错误漏洞，该漏洞源于多个签名验证路径中，从SpcIndirectDataContent结构复制摘要值到固定大小栈缓冲区时未验证源长度，可能导致栈缓冲区溢出。

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