CVE-2026-6091: Partial-chain verification accepts untrusted intermediate as trust anchor

CSIRTS triage

What

Partial-chain verification accepts untrusted intermediate as trust anchor.

Who is affected

Deployments using the affected verification process.

Urgency

Remediation is important due to the medium severity and potential trust issues.

Action

Review and update verification processes.

AI-assisted analysis generated from the source advisory — verify against the original.

Details

Source

Microsoft Security Response Center (INTL · vendor-psirt · site)

Severity

medium — CVSS 6.5

Published

2026-06-09

Exploitation

Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-6091

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

• Low exploitation riskCVE-2026-60910.12% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 2% of all scored CVEs.

Referenced CVEs

More from Microsoft Security Response Center

• highCVE-2026-12064: proto-default skips SSH verification2026-07-02
• unknownCVE-2026-14125: Chromium: CVE-2026-14125 Uninitialized Use in ANGLE2026-07-02
• mediumCVE-2026-57987: Microsoft Edge (Chromium-based) Spoofing Vulnerability2026-07-02
• unknownCVE-2026-13775: Chromium: CVE-2026-13775 Use after free in GPU2026-07-02
• unknownCVE-2026-13779: Chromium: CVE-2026-13779 Use after free in Chromoting2026-07-02