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CVE-2026-109399— SWUpdate through 2026.05.1 CMS Signature Verification Bypass via Embedded Intermediates

Quick assessment

Affected
sbabic swupdate
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

SWUpdate（版本在 2026.05.1 及之前）在 crypto/swupdate_cms_verify_openssl.c 中存在不正确的证书验证漏洞，该漏洞会信任嵌入在 CMS SignedData 中的不受信任的 X.509 证书以用于构建证书链。持有相同根证书下发放的兄弟中间证书签名密钥的攻击者，可以将该中间证书嵌入签名中，从而安装恶意更新。

CVSS 8.1 · High EPSS 0.21% · P10

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
sbabic swupdate ≤ 2026.05.1 affected
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I. Basic Information for CVE-2026-109399

Vulnerability Information
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Vulnerability Title
SWUpdate through 2026.05.1 CMS Signature Verification Bypass via Embedded Intermediates
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
证书验证不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
sbabic swupdate 0 ~ 2026.05.1 -

II. Public POCs for CVE-2026-109399

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III. Intelligence Information for CVE-2026-109399

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Patches & Fixes for CVE-2026-109399 (3)

Vendor Advisories for CVE-2026-109399 (1)

IV. Related Vulnerabilities

Same product: swupdate
Same vendor: sbabic
Same weakness: CWE-295

V. Comments for CVE-2026-109399

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