Stack Buffer Overflow in osslsigncode Affects Verification of Signed Files

CVE-2026-39853

What is CVE-2026-39853?

The osslsigncode tool, responsible for Authenticode signing and timestamping, is susceptible to a stack buffer overflow vulnerability present in various signature verification processes. This issue occurs when the tool processes a PKCS#7 signature and improperly copies a digest value from a SpcIndirectDataContent structure into a fixed-size stack buffer, without verifying the length of the source. Attackers can exploit this flaw by crafting a malicious signed file that includes an oversized digest field in the SpcIndirectDataContent. When users attempt to verify such files using osslsigncode, the faulty unbounded memory copy can lead to stack buffer overflow, compromising the integrity of the stack and potentially executing arbitrary code. This vulnerability has been addressed in osslsigncode version 2.12.

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