Craft CMS 5.0.0-RC1 before 5.10.12 Behavior Injection RCE (CVE-2026-86730) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-86730

Craft CMS 5.0.0-RC1 before 5.10.12 Behavior Injection RCE

Answer in brief

CVE-2026-86730 records a Unknown severity vulnerability in Craft CMS 5.0.0-RC1 before 5.10.12 Behavior Injection RCE. The current sources do not mark it as known exploited. The current feed maps craftcms/cms (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 8, 2026Updated Sep 8, 2026Source checked Sep 8, 2026First seen by HOL Sep 8, 2026Material review Sep 8, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps craftcms/cms (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
craftcms/cmsgeneric	>=5.0.0-RC1 <5.10.12	5.10.12

Recommended response

Check inventory. Check lockfiles and deployed manifests for craftcms/cms.
Review the reported fix. Update craftcms/cms to 5.10.12 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 8, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 8, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 8, 2026

Sources and claim methodology

Upstream source description

Craft CMS versions before 5.10.12 fail to properly cleanse string-typed field-layout elements, allowing authenticated control-panel users to inject Yii2 behavior attachments and event handlers. Attackers can post field-layout tab elements as JSON strings to bypass cleanse validation, then trigger arbitrary object instantiation and code execution through Craft::createObject().

Quoted source text, attributed separately from HOL analysis.