osslsigncode has a Stack Buffer Overflow via Unbounded Digest Copy During Signature Verification

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Summary

CVECVE-2026-39853
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-09 16:16:31 UTC
Updated2026-04-09 16:16:31 UTC
Descriptionosslsigncode 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.

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from [email protected]

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

Problem Types: CWE-121 | CWE-787 | CWE-121 CWE-121: Stack-based Buffer Overflow | CWE-787 CWE-787: Out-of-bounds Write

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

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

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mtrojnar Osslsigncode affected < 2.12 Not specified

References

ReferenceSourceLinkTags
github.com/mtrojnar/osslsigncode/releases/tag/2.12 [email protected] github.com
github.com/mtrojnar/osslsigncode/commit/cbee1e723c5a8547302bd841ad9943ed... [email protected] github.com
github.com/mtrojnar/osslsigncode/security/advisories/GHSA-hx87-8754-xvh4 [email protected] github.com
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