CVE-2026-109399
Received Received - Intake

Improper Certificate Validation in SWUpdate CMS SignedData

Publication date: 2026-10-12

Last updated on: 2026-10-12

Assigner: VulnCheck

Description
SWUpdate through 2026.05.1 contains an improper certificate validation vulnerability in crypto/swupdate_cms_verify_openssl.c that trusts untrusted X.509 certificates embedded in CMS SignedData for chain building. Attackers holding a signing key from a sibling intermediate under the same root can embed that intermediate in the signature to install malicious updates.

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Meta Information

Published
2026-10-12
Last Modified
2026-10-12
Generated
2026-10-12
AI Q&A
2026-10-12
EPSS Evaluated
N/A
NVD
CVE-2026-109399
EUVD
EUVD-2026-97496

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
sbabic swupdate 0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-295 The product does not validate, or incorrectly validates, a certificate.

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Executive Summary

SWUpdate through 2026.05.1 has an improper certificate validation flaw in its OpenSSL-based CMS verification. It incorrectly trusts untrusted X.509 certificates embedded in CMS SignedData during chain building. Attackers with a signing key from a sibling intermediate under the same root can embed that intermediate certificate to bypass validation and install malicious updates.

Detection Guidance

To detect this vulnerability, inspect SWUpdate configurations for the presence of the CONFIG_CMS_IGNORE_ADDITIONAL_CERTS option. Check if the system uses SWUpdate versions up to 2026.05.1. Review update files for embedded X.509 certificates in CMS SignedData structures. Use OpenSSL commands to verify signatures and certificate chains manually.

Impact Analysis

This vulnerability allows attackers to bypass certificate validation and install malicious software updates on affected systems. If exploited, it could lead to unauthorized code execution, data breaches, or full system compromise. Users relying on SWUpdate for firmware or software updates are at risk of installing tampered updates.

Compliance Impact

This vulnerability could violate compliance requirements that mandate secure update mechanisms and integrity checks, such as GDPR's security principles or HIPAA's integrity safeguards. Failure to prevent unauthorized updates may result in non-compliance, potential data breaches, and regulatory penalties.

Mitigation Strategies

Update SWUpdate to version 2026.05.1 or later to address the improper certificate validation issue. Ensure all X.509 certificates in CMS SignedData are properly validated and restrict intermediate certificates to trusted chains only.

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