Quick answers
- Is CVE-2026-109399 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-109399 being exploited in the wild.
- How severe is CVE-2026-109399?
- High severity, with a CVSS score of 8.1, published 12 October 2026.
- Which products and versions are affected?
- SWUpdate through 2026.05.1.
- Is there a fix for CVE-2026-109399?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-109399 attacked?
- It is attacked over the network, in device firmware.
- Am I affected by CVE-2026-109399?
- Check whether you run SWUpdate at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is an improper certificate validation flaw in crypto/swupdate_cms_verify_openssl.c where the CMS signature verification process trusts untrusted X.509 certificates embedded in SignedData structures for chain building. An attacker possessing a private key from a sibling intermediate certificate under the same root CA can embed that intermediate in the malicious signature to bypass validation and install unauthorized firmware updates.
Affected products
- SWUpdate through 2026.05.1
Timeline
- 2026-10-12: disclosed