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Forminator CVE-2026-66583

CRITICAL
Deserialization of Untrusted Data (CWE-502)
2026-08-20 Patchstack
9.8
CVSS 3.1 · Vendor: Patchstack
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Severity by source

Vendor (Patchstack) PRIMARY
9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vuln.today AI
9.8 CRITICAL

Unauthenticated (PR:N) network form input reaches unsafe deserialization with no user interaction; object injection can yield full C/I/A impact via a gadget chain, though impact is chain-dependent.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (Patchstack).

CVSS VectorVendor: Patchstack

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

2
Analysis Generated
Aug 20, 2026 - 12:35 vuln.today
CVE Published
Aug 20, 2026 - 12:06 cve.org
CRITICAL 9.8

DescriptionCVE.org

Unauthenticated PHP Object Injection in Forminator <= 1.57.0 versions.

AnalysisAI

Unauthenticated PHP Object Injection in the Forminator WordPress plugin (WPMU DEV) affects all versions up to and including 1.57.0, letting remote attackers submit crafted serialized data that is deserialized without validation to potentially achieve arbitrary object instantiation and, with a suitable POP gadget chain, remote code execution. The vulnerability carries a CVSS 9.8 rating with a fully unauthenticated network vector and complete confidentiality, integrity, and availability impact. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Identify public WordPress site running Forminator ≤1.57.0
Delivery
Craft serialized PHP object payload
Exploit
Submit payload via form endpoint
Execution
Plugin deserializes untrusted input
Persist
POP gadget chain instantiates objects
Impact
Achieve code execution or file write

Vulnerability AssessmentAI

Exploitation Exploitation requires that a vulnerable Forminator form (version <= 1.57.0) be reachable and accept the input parameter that flows into the unsafe deserialization call; no authentication is needed (PR:N) and no user interaction is required (UI:N), so any public-facing form endpoint is a candidate. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) describes a worst-case remotely exploitable, unauthenticated, low-complexity flaw with full triple impact, yielding a 9.8 base score, and the unauthenticated nature combined with WordPress's large attack surface makes this a genuine priority for exposed installations. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario A remote, unauthenticated attacker locates a public WordPress site running a vulnerable Forminator form, then submits a form request whose input contains a crafted PHP serialized object payload. Because the plugin deserializes this input without validation, the attacker-supplied objects are instantiated and, if a compatible gadget chain exists in the site's loaded classes, magic methods are triggered to escalate toward file manipulation or code execution. …
Remediation Upgrade Forminator to the vendor's fixed release above 1.57.0 as soon as it is available; the exact patched version is not confirmed in the provided data, so consult the Patchstack advisory (https://patchstack.com/database/wordpress/plugin/forminator/vulnerability/wordpress-forminator-plugin-1-57-0-php-object-injection-vulnerability) and the WPMU DEV changelog for the specific fixed version before deploying. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, audit all WordPress installations to identify those running Forminator plugin version 1.57.0 or earlier and prioritize internet-facing instances for immediate action. …

Sign in for detailed remediation steps and compensating controls.

Threat intelligence, references, and detailed analysis are available after sign-in.

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CVE-2026-66583 vulnerability details – vuln.today

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