osslsigncode has an Integer Underflow in PE Page Hash Calculation Can Cause Out-of-Bounds Read

osslsigncode is a tool that implements Authenticode signing and timestamping. Prior to 2.13, an integer underflow vulnerability exists in osslsigncode version 2.12 and earlier in the PE page-hash computation code (pe_page_hash_calc()). When page hash processing is performed on a PE file, the function subtracts hdrsize from pagesize without first validating that pagesize >= hdrsize. If a malicious PE file sets SizeOfHeaders (hdrsize) larger than SectionAlignment (pagesize), the subtraction underflows and produces a very large unsigned length. The code allocates a zero-filled buffer of pagesize bytes and then attempts to hash pagesize - hdrsize bytes from that buffer. After the underflow, this results in an out-of-bounds read from the heap and can crash the process. The vulnerability can be triggered while signing a malicious PE file with page hashing enabled (-ph), or while verifying a malicious signed PE file that already contains page hashes. Verification of an already signed file does not require the verifier to pass -ph. This vulnerability is fixed in 2.13.

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

跨界内存读

osslsigncode 数字错误漏洞

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 2.13之前版本存在数字错误漏洞，该漏洞源于PE页面哈希计算代码中，在未验证pagesize大于等于hdrsize的情况下执行减法操作，可能导致整数下溢和越界读取。

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