What is the CVSS score of EUVD-2026-63831?

EUVD-2026-63831 has a contested CVSS base score of 5.4 from a third party (e.g. CISA-ADP), while the vendor rates it Medium. vuln.today uses the vendor rating as authoritative.

Apache CloudStack EUVD-2026-63831

| CVE-2026-66797 MEDIUM

Improper Access Control (CWE-284)

2026-08-21 apache

GHSA-6777-p72p-347g

Apache Authentication Bypass Apache Cloudstack

Medium

Disputed · 5.4 Vendor: apache

Severity by source

Sources disagree (Low–High)

Vendor (apache) PRIMARY

5.4 LOW

AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

vuln.today AI

5.4 MEDIUM

Network-accessible API requiring authenticated low-privilege user (PR:L); no complexity barriers; impact limited to annotation confidentiality and integrity with no availability effect.

3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

Red Hat

8.5 HIGH

qualitative

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorVendor: apache

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Lifecycle Timeline

Analysis Generated

Aug 21, 2026 - 09:05 vuln.today

DescriptionCVE.org

Improper access control in CloudStack's annotation functionality allows unauthorized comment creation and disclosure.

The addAnnotation and listAnnotation APIs perform an ownership check when an entity's UUID is specified, but fail to honor its result correctly. This lets any authenticated user write annotations to, and disclose existing annotations/comments on, an entity they don't own by simply supplying its UUID.

This issue affects Apache CloudStack: from 4.15.0.0 through 4.20.3.0 and from 4.21.0.0 through 4.22.1.0.

Users are recommended to upgrade to version 4.20.3.1 or 4.22.1.1 or later, which fixes the issue.

AnalysisAI

Improper access control in Apache CloudStack's annotation APIs (addAnnotation and listAnnotation) allows any authenticated user to read and write annotations on entities they do not own. The APIs perform an ownership check when an entity UUID is supplied but fail to enforce the result of that check, reducing authorization to a formality that any authenticated user can bypass. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access

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Vulnerability AssessmentAI

Exploitation	Exploitation requires a valid authenticated session to the Apache CloudStack API; unauthenticated access is not sufficient. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment	No CVSS vector was provided by NVD or the vendor, so formal metric comparison is not possible. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario	Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation	Vendor-released patch: 4.20.3.1 (for the 4.20.x branch) and 4.22.1.1 (for the 4.22.x branch). … Detailed patch versions, workarounds, and compensating controls in full report.