CVE-2026-91846: MISP Collection Element Add Missing Authorization on Referenced Object UUID

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?

0.4%

EPSS score, percentile 28.7 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 introduces a dedicated __assertCanUseElements() authorization guard that is invoked in the beforeSave callback of the add() CRUD path (covering both form and … Full textSolution from the CVE record.

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

Advisories and patches (1)

Which versions are affected?

Affected

• before 2.5.46

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 introduces a dedicated __assertCanUseElements() authorization guard that is invoked in the beforeSave callback of the add() CRUD path (covering both form and REST submission) and in addElementToCollection(). For each element UUID, the method resolves the element type (deducing it if the caller omitted the field, preventing bypass by omission) and performs an ACL-aware lookup: for Events it calls fetchSimpleEvent() scoped to the current user, and for GalaxyClusters it calls fetchGalaxyClusters() with the user context. If the object does not exist or the caller lacks access, a NotFoundException is raised and the save is aborted. This ensures that no collection element can reference an object the caller is not authorized to read.

Advisories and patches

• 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

Affected versions of MISP allow a collection element to be created from a bare UUID without consistently checking whether the acting user is allowed to access the referenced object. The commit explains that collection elements themselves only store UUIDs, while the collection view later resolves those UUIDs into their underlying objects. Before this fix, the generic add() path could therefore p…

Summary: CVE record, as of 29 Oct 2026.

• CISA has not added CVE-2026-91846 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
• The CVE record was published on 15 Sep 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 0.4% (percentile 28.7), 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 Collection Element Add Missing Authorization on Referenced Object UUID

Affected versions of MISP allow a collection element to be created from a bare UUID without consistently checking whether the acting user is allowed to access the referenced object. The commit explains that collection elements themselves only store UUIDs, while the collection view later resolves those UUIDs into their underlying objects. Before this fix, the generic add() path could therefore persist a UUID for an Event or Galaxy Cluster that the caller could not normally read. The patch explicitly notes that this made collections a way to reference another organisation’s private data and had caused disclosure of organisation-only events in the beta collection view. The fix centralizes authorization in __assertCanUseElements(). Event UUIDs are validated through Event::fetchSimpleEvent() under the current user’s ACL, while Galaxy Cluster UUIDs are checked through GalaxyCluster::fetchGalaxyClusters(). The check is applied both to the CRUD add() path and to addElementToCollection(). Version affected: ≤2.5.45

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

Timeline