mtrojnar osslsigncode up to 2.11 stack-based overflow

Summaryinfo

A vulnerability was found in mtrojnar osslsigncode up to 2.11. It has been classified as critical. This issue affects some unknown processing. Performing a manipulation results in stack-based overflow. This vulnerability was named CVE-2026-39853. The attack may be initiated remotely. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in mtrojnar osslsigncode up to 2.11. It has been classified as critical. This affects an unknown code block. The manipulation with an unknown input leads to a stack-based overflow vulnerability. CWE is classifying the issue as CWE-121. A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function). This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-39853 since 04/07/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available.

Upgrading to version 2.12 eliminates this vulnerability.

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Productinfo

Vendor

• mtrojnar

Name

• osslsigncode

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4
• 2.5
• 2.6
• 2.7
• 2.8
• 2.9
• 2.10
• 2.11

Website

• Product: https://github.com/mtrojnar/osslsigncode/

CPE 2.3info

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CPE 2.2info

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