CVE-2026-39853: Osslsigncode Project Osslsigncode

High severity, CVSS 7.8. EPSS: 0.2% chance of exploitation in the next 30 days.

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.

Affected products

• Osslsigncode Project Osslsigncode: before 2.12 (fixed in 2.12)

Published 2026-04-09. Last modified 2026-06-17.