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

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Summary

CVECVE-2026-39855
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-09 17:16:29 UTC
Updated2026-04-09 17:16:29 UTC
Descriptionosslsigncode 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.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

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

Problem Types: CWE-125 | CWE-190 | CWE-191 | CWE-125 CWE-125: Out-of-bounds Read | CWE-190 CWE-190: Integer Overflow or Wraparound | CWE-191 CWE-191: Integer Underflow (Wrap or Wraparound)

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
3.1CNADECLARED5.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mtrojnar Osslsigncode affected < 2.13 Not specified

References

ReferenceSourceLinkTags
github.com/mtrojnar/osslsigncode/security/advisories/GHSA-76vv-x5rr-q3mr [email protected] github.com
github.com/mtrojnar/osslsigncode/commit/2a5409b7c4b6c6fad2b093531e8fea6c... [email protected] github.com
github.com/mtrojnar/osslsigncode/releases/tag/2.13 [email protected] github.com
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