CVE-2026-56424: Broken access control in MISP core allows cross-organization unauthorized modification or deletion of analyst data, event reports, collections, templates, and decaying models

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?

0.5%

EPSS score, percentile 44.3 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?

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

Advisories and patches (5)

Which versions are affected?

Affected

• 2.5.41 and earlier

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

Advisories and patches

• github.com (Patch)
• github.com (Patch)
• github.com (Patch)
• github.com (Patch)
• github.com (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.

Versions not listed are: unaffected.

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

About this vulnerability

MISP core contained multiple broken access-control flaws where authorization checks were performed against the wrong entity, or where ownership/editability checks were missing on write paths. In affected subsystems, a lower-privileged authenticated user with the relevant feature permission could cause the application to authorize one object but mutate another, or could modify objects that were me…

Summary: CVE record, as of 29 Oct 2026.

• CISA has not added CVE-2026-56424 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
• The CVE record was published on 22 Jun 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 0.5% (percentile 44.3), 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

Broken access control in MISP core allows cross-organization unauthorized modification or deletion of analyst data, event reports, collections, templates, and decaying models

MISP core contained multiple broken access-control flaws where authorization checks were performed against the wrong entity, or where ownership/editability checks were missing on write paths. In affected subsystems, a lower-privileged authenticated user with the relevant feature permission could cause the application to authorize one object but mutate another, or could modify objects that were merely visible rather than editable by the user’s organization. The affected paths included: * Event Reports tag removal: the route-authorized report could differ from the report ID used for tag detachment, enabling cross-organization tag removal from another event report * Collection Elements bulk deletion: bulk deletion authorized against a collection whose ID matched the collection-element row ID, rather than the element’s actual parent collection, enabling deletion of elements from collections the user did not own. * Analyst Data capture/update: nested analyst data updates could overwrite an existing record without applying the normal canEditAnalystData ownership check, enabling cross-organization overwrite of analyst data records. * Template Elements editing: editing authorized against a template whose ID matched the template-element ID, rather than the element’s actual parent template, enabling unauthorized edits to another organization’s template elements. * Decaying Model editing and mappings: write paths loaded models using view-scope access but did not verify edit ownership, enabling users to edit or remap visible models owned by another organization.  Successful exploitation could allow an authenticated user with subsystem-specific permissions to perform unauthorized cross-organization modifications or deletions of MISP data, resulting in integrity loss, unauthorized tampering with shared intelligence, and disruption of analyst workflows.

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

Timeline