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TI-2026-28735 Aliases CVE-2026-39853

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

Priority LOW 35CWE-121Published · Updated

Key facts

Attack vector
Local
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-121 and the CVSS impact.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00166 5th percentileScored 2026-11-07
Fix Fixed osslsigncode (mtrojnar): 2.12

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
mtrojnarosslsigncodebefore 2.122.12Patch availableCNA
  • osslsigncode Vendormtrojnar Affected before 2.12 Fixed in 2.12 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:osslsigncode_project:osslsigncode:*:*:*:*:*:*:*:*before 2.12Vulnerablemtrojnar
  • cpe:2.3:a:osslsigncode_project:osslsigncode:*:*:*:*:*:*:*:* Versions before 2.12 Vulnerable ·mtrojnar

Remediation

  • Fix · CNA osslsigncode (mtrojnar) Fixed in 2.12

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-39853

References

Patch 1

Advisory 1

Other 1

  • TI-2025-43157 An issue in mtrojnar Osslsigncode affected at v2.10 and before allows a remote attacker… CVSS 3.1CRITICAL 9.8
  • TI-2023-18242 Buffer Overflow vulnerability in mtrojnar osslsigncode v.2.3 and before allows a local… CVSS 3.1HIGH 7.8
  • TI-2026-28737 osslsigncode has an Out-of-Bounds Read via Unvalidated Section Bounds in PE Page Hash Calculation CVSS 3.1MEDIUM 5.5
  • TI-2026-28736 osslsigncode has an Integer Underflow in PE Page Hash Calculation Can Cause Out-of-Bounds Read CVSS 3.1MEDIUM 5.5

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences