CVE-2026-103239: MISP Tag Collection Save Allows Privilege Escalation via Sibling Model Injection

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?

0.3%

EPSS score, percentile 17.1 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

8.6 High

CVSS v4.0 base score, given by the CNA

What should I do?

The fix replaces the bulk-association save call with an explicit two-step process: first … 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 2.5.48

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 replaces the bulk-association save call with an explicit two-step process: first, only the TagCollection data is extracted from the request and saved via a plain save() operation that does not write belongsTo siblings; second, tag association rows are persisted individually in a controlled loop. This ensures that any User, Organisation, or other sibling model data present in the request payload is silently discarded and never reaches the database, eliminating the privilege escalation path.

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

MISP contains a privilege escalation vulnerability in the tag collection creation and editing functionality. The affected actions accepted the full HTTP request payload and passed it to a bulk-association save operation, which writes not only the intended tag collection record but also any associated model data present in the payload. A user holding the tag editor permission could craft a reques…

Summary: CVE record, as of 29 Oct 2026.

• CISA has not added CVE-2026-103239 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
• The CVE record was published on 30 Sep 2026.
• The CVE record carries a CVSS v4.0 base score of 8.6 (High), given by its CNA.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.3% (percentile 17.1), 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 total.
• 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 Tag Collection Save Allows Privilege Escalation via Sibling Model Injection

MISP contains a privilege escalation vulnerability in the tag collection creation and editing functionality. The affected actions accepted the full HTTP request payload and passed it to a bulk-association save operation, which writes not only the intended tag collection record but also any associated model data present in the payload. A user holding the tag editor permission could craft a request that includes additional model data (such as User or Organisation records) alongside the tag collection fields. Because the save operation processed all associated models indiscriminately, the injected sibling records were written to the database, enabling the attacker to modify or create privileged accounts and escalate to site administrator. Preconditions: - An authenticated account with the tag editor permission (perm_tag_editor) - Network access to the MISP instance Impact: - Unauthorized creation or modification of User and Organisation records - Privilege escalation from tag editor to site administrator Affected versions: < 2.5.48

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

Timeline