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Full vulnerability report · 2026
CVE-2026-88915High confidence

MISP Event Template Instantiation Bypasses Sharing Group and Tagging Authorization

MISP · MISP

7.1HighCVSS 4.0
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-75409

No EUVD known-exploited evidence

Affected versions of MISP do not consistently enforce the acting user's authorization when instantiating event templates. For templates using distribution = 4, the template can specify a sharing_group_id. The instantiation path passed that value into event creation without verifying that the user instantiating the template was actually permitted to use the selected sharing group. The commit notes that Event::_add() only performed its own sharing-group authorization in another code path, leaving template instantiation able to write the identifier directly. The same instantiation path also attached template-specified tags without checking the user's normal tagging permissions. In addition, it hardcoded local => 0, meaning tags marked local_only could be attached globally and consequently propagate through synchronization or export, contrary to their intended restriction. The fix adds explicit SharingGroup::canUse() authorization for the acting user, applies the same tag-modification checks used by normal event tagging, and ensures local_only tags are attached locally. Version affected: ≤2.5.45

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
7.1 · CVSS 4.0
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

Affected versions of MISP do not consistently enforce the acting user's authorization when instantiating event templates. For templates using distribution = 4, the template can specify a sharing_group_id. The instantiation path passed that value into event creation without verifying that the user instantiating the template was actually permitted to use the selected sharing group. The commit notes that Event::_add() only performed its own sharing-group authorization in another code path, leaving template instantiation able to write the identifier directly. The same instantiation path also attached template-specified tags without checking the user's normal tagging permissions. In addition, it hardcoded local => 0, meaning tags marked local_only could be attached globally and consequently propagate through synchronization or export, contrary to their intended restriction. The fix adds explicit SharingGroup::canUse() authorization for the acting user, applies the same tag-modification checks used by normal event tagging, and ensures local_only tags are attached locally. Version affected: ≤2.5.45

What

Affected versions of MISP do not consistently enforce the acting user's authorization when instantiating event templates. For templates using distribution = 4, the template can specify a sharing_group_id. The instantiation path passed that value into event creation without verifying that the user instantiating the template was actually permitted to use the selected sharing group. The commit notes that Event::_add() only performed its own sharing-group authorization in another code path, leaving template instantiation able to write the identifier directly. The same instantiation path also attached template-specified tags without checking the user's normal tagging permissions. In addition, it hardcoded local => 0, meaning tags marked local_only could be attached globally and consequently propagate through synchronization or export, contrary to their intended restriction. The fix adds explicit SharingGroup::canUse() authorization for the acting user, applies the same tag-modification checks used by normal event tagging, and ensures local_only tags are attached locally. Version affected: ≤2.5.45

Why

The application reaches a protected operation without first confirming that the requester is authorised.

How

An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

Affected versions of MISP do not consistently enforce the acting user's authorization when instantiating event templates. For templates using distribution = 4, the template can specify a sharing_group_id. The instantiation path passed that value into event creation without verifying that the user instantiating the template was actually permitted to use the selected sharing group. The commit notes that Event::_add() only performed its own sharing-group authorization in another code path, leaving template instantiation able to write the identifier directly. The same instantiation path also attached template-specified tags without checking the user's normal tagging permissions. In addition, it hardcoded local => 0, meaning tags marked local_only could be attached globally and consequently propagate through synchronization or export, contrary to their intended restriction. The fix adds explicit SharingGroup::canUse() authorization for the acting user, applies the same tag-modification checks used by normal event tagging, and ensures local_only tags are attached locally. Version affected: ≤2.5.45

Why

The application reaches a protected operation without first confirming that the requester is authorised.

How

An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Missing Authorization → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
Low: a basic authenticated account is required
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Not a CVSS 4.0 base metric
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-862 ↗

CWE-862: Missing Authorization. The product does not perform an authorization check when an actor attempts to access a resource or perform an action.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

Common Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.ATNoneAttack requirements: No additional deployment or execution condition is required.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.VCNoneVulnerable-system confidentiality: No direct loss is represented by this metric.VIHighVulnerable-system integrity: A successful attack can cause a major loss.VANoneVulnerable-system availability: No direct loss is represented by this metric.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SANoneSubsequent-system availability: No direct loss is represented by this metric.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkCWE-862
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-75409Official EUVD mapping

Affected versions of MISP do not consistently enforce the acting user's authorization when instantiating event templates. For templates using distribution = 4, the template can specify a sharing_group_id. The instantiation path passed that value into event creation without verifying that the user instantiating the template was actually permitted to use the selected sharing group. The commit notes that Event::_add() only performed its own sharing-group authorization in another code path, leaving template instantiation able to write the identifier directly. The same instantiation path also attached template-specified tags without checking the user's normal tagging permissions. In addition, it hardcoded local => 0, meaning tags marked local_only could be attached globally and consequently propagate through synchronization or export, contrary to their intended restriction. The fix adds explicit SharingGroup::canUse() authorization for the acting user, applies the same tag-modification checks used by normal event tagging, and ensures local_only tags are attached locally. Version affected: ≤2.5.45

Official EUVD record ↗
BSI · German · WID-SEC-2026-3314MISP: Mehrere Schwachstellen ermöglichen Manipulation von Dateien

Ein entfernter, authentisierter Angreifer kann mehrere Schwachstellen in MISP ausnutzen, um Dateien zu manipulieren.

Official advisory ↗
CSIRT Italia · Italian · risolte-vulnerabilita-in-misp-projectRisolte vulnerabilità in MISP Project

Aggiornamenti di sicurezza sanano due vulnerabilità, di cui una con gravità "alta", in MISP Project, nota piattaforma collaborativa di cyber threat intelligence. Tale vulnerabilità, qualora sfruttata, potrebbe consentire ad un utente malintenzionato di eludere le restrizioni di sicurezza sui sistemi interessati.

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
MISP: ≤ 2.5.45
Fixed
An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 10 Sept 2026 · Last source change 10 Sept 2026, 17:33 UTC · CWE-862 · Missing Authorization

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-09-11
European sourceENISA EUVD · EUVD-2026-75409
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD not scheduled

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. ENISA EUVD mappingEUVD-2026-75409 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2026-75409"}
    ENISA EUVD ↗
  2. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
ENISA EUVD · EUVD-2026-75409↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-88915 · cve.blacktree.nl