CVE-2026-103659: MISP: Object Distribution ACL Bypass via Event Flattening Exposes Organisation-Only Attributes

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of 29 Oct 2026. If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?

0.2%

EPSS score, percentile 13.6 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

7.1 High

CVSS v4.0 base score, given by the CNA

What should I do?

The fix re-applies the object distribution and sharing-group ACL as a subquery condition on the Attribute.object_id field whenever the flatten option is active. Full textSolution from the CVE record.

CISA has set no required action, because the vulnerability is not in KEV.

Advisories and patches (2)

Which versions are affected?

Affected

• before 2.5.48

Versions by product

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026; CVE List, as of 29 Oct 2026. About the data.

What to do

Solution (from the CVE record)

The fix re-applies the object distribution and sharing-group ACL as a subquery condition on the Attribute.object_id field whenever the flatten option is active. This ensures that attributes belonging to objects the caller is not authorized to see are excluded from the flattened result set. The second commit refines the gate to use only the distribution ACL condition (correlated on Object.id) rather than the entire Object contain, preventing soft-delete state from incorrectly filtering attributes for the event owner.

Advisories and patches

• Security patch (Patch)
• Security patch (Patch)

This summary is based on the CVE record as of 29 Oct 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

As listed in the CVE record.

Source: CVE List, as of 29 Oct 2026. About the data.

About this vulnerability

MISP contains an authorization bypass in the event flattening feature. When a user requests an event with the flatten option enabled, the application removes the Object containment from the query and returns object attributes as top-level event attributes. In doing so, the object-level distribution and sharing-group access control check was not re-applied to those attributes. As a result, a user…

Summary: CVE record, as of 29 Oct 2026.

• CISA has not added CVE-2026-103659 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
• The CVE record was published on 1 Oct 2026.
• The CVE record carries a CVSS v4.0 base score of 7.1 (High), given by its CNA.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.2% (percentile 13.6), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
• CISA's SSVC assessment in the CVE record: exploitation none, automatable no, technical impact partial.
• The credits in the CVE record name Anthropic (Claude) as finder.

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; CVE List, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026. About the data.

Description

MISP: Object Distribution ACL Bypass via Event Flattening Exposes Organisation-Only Attributes

MISP contains an authorization bypass in the event flattening feature. When a user requests an event with the flatten option enabled, the application removes the Object containment from the query and returns object attributes as top-level event attributes. In doing so, the object-level distribution and sharing-group access control check was not re-applied to those attributes. As a result, a user who can view a community-distributed event could retrieve attributes belonging to organisation-only objects (distribution level 0) or objects restricted to a specific sharing group, even though the user's organisation does not have access to those objects. This constitutes an unauthorized disclosure of sensitive threat intelligence data. A secondary issue was introduced by the initial remediation: the fix reused the full Object contain conditions (including soft-delete state) as the gate for flattened attributes, causing an event owner requesting deleted attributes to lose all attributes whose parent object was still live. The final fix isolates the distribution ACL condition as the sole gate. Preconditions: - An authenticated user with access to a community-distributed event - The event contains at least one object with a distribution level or sharing group that restricts access beyond the event's own distribution Impact: - Unauthorized disclosure of attributes belonging to restricted objects - Potential exposure of organisation-specific threat intelligence to other organisations Affected versions: <2.5.48

Source: CVE List, as of 29 Oct 2026. About the data.

Timeline