CVE-2026-39856 MEDIUM

CVE-2026-39856: osslsigncode has an Out-of-Bounds Read via Unvalidated Section Bounds in PE Page Hash Calculation

Vendor Mtrojnar
Product osslsigncode
Weakness CWE-125
Published April 9, 2026
Last update April 13, 2026

CVSS base score

5.5/10
Attack vector Local
Attack complexity Low
Privileges required None
User interaction Required
Confidentiality None
Integrity None

CVSS vector

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

What the vulnerability does

01Description

osslsigncode is a tool that implements Authenticode signing and timestamping. Prior to 2.13, an out-of-bounds read vulnerability exists in osslsigncode version 2.12 and earlier in the PE page-hash computation code (pe_page_hash_calc()). When processing PE sections for page hashing, the function uses PointerToRawData and SizeOfRawData values from section headers without validating that the referenced region lies within the mapped file. An attacker can craft a PE file with section headers that point beyond the end of the file. When osslsigncode computes page hashes for such a file, it may attempt to hash data from an invalid memory region, causing an out-of-bounds read and potentially crashing 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.

Key dates

02Disclosure timeline

April 9, 2026 CVE published
April 13, 2026 Record updated