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Formie: Unauthenticated users can overwrite incomplete submissions via submit action

High severity GitHub Reviewed Published Jul 9, 2026 in verbb/formie • Updated Sep 23, 2026

Package

composer verbb/formie (Composer)

Affected versions

>= 3.0.0, < 3.1.31
< 2.2.23

Patched versions

3.1.31
2.2.23

Description

Impact

The anonymous front-end action formie/submissions/submit (SubmissionsController::actionSubmit) trusted a client-supplied submissionId when loading an incomplete submission, with no session binding, ownership check, or edit token validation.

An unauthenticated attacker could enumerate sequential submission IDs and overwrite or hijack another user's in-progress (multi-page / save-for-later) submission. Tampered data could be persisted and forwarded via notifications and integrations when the submission was completed.

Completed submissions were not affected (isIncomplete=true filter). This is an incomplete remediation of GHSA-pgxq-p76c-x9cg, which added edit-token validation to save-submission but not to submit.

Patches

Fixed in 3.1.31 (Craft 5) and 2.2.23 (Craft 4).

When resuming an existing submission on a site request, the submission ID must match the session-bound submission (Form::getCurrentSubmission()) or a valid submissionEditToken when editingSubmission is set. Cross-form submission ID reuse is also rejected.

Workarounds

No reliable workaround without upgrading. Disabling multi-page forms or save-for-later reduces exposure but does not remove the vulnerability.

References

@engram-design engram-design published to verbb/formie Jul 9, 2026
Published to the GitHub Advisory Database Sep 23, 2026
Reviewed Sep 23, 2026
Last updated Sep 23, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(22nd percentile)

Weaknesses

Authorization Bypass Through User-Controlled Key

The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data. Learn more on MITRE.

Missing Authorization

The product does not perform an authorization check when an actor attempts to access a resource or perform an action. Learn more on MITRE.

CVE ID

CVE-2026-76087

GHSA ID

GHSA-584p-f93j-wpgc

Source code

Credits

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