CVE-2025-23041: Umbraco Forms Information Disclosure Flaw

CVE-2025-23041 Overview

CVE-2025-23041 is an improper input validation vulnerability in Umbraco Forms, a web form framework built for the NuGet ecosystem. Character limits configured by editors for short and long answer fields are enforced only on the client side. The server accepts form submissions without validating the configured length constraints. Attackers can bypass these limits by submitting crafted requests directly to the server, undermining data integrity controls set by content editors. The issue is tracked under [CWE-20] Improper Input Validation and affects multiple supported release lines of Umbraco Forms.

Critical Impact
Remote unauthenticated attackers can submit form data that exceeds editor-defined character limits, bypassing client-side controls and impacting integrity of stored form submissions.

Affected Products

Umbraco Forms versions prior to 8.13.16
Umbraco Forms versions prior to 10.5.7 and 13.2.2
Umbraco Forms versions prior to 14.1.2

Discovery Timeline

2025-01-14 - CVE CVE-2025-23041 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-23041

Vulnerability Analysis

Umbraco Forms allows content editors to define character limits on short answer and long answer field types. These limits are intended to constrain the length of user-submitted data at both the presentation and persistence layers. The framework enforces the limits only through client-side JavaScript validation. The server-side submission handler does not re-validate that field content respects the configured maximums before processing or storing the response. This is a classic trust-the-client design flaw that maps to [CWE-20] Improper Input Validation.

Root Cause

The root cause is a missing server-side validation step. Length constraints defined in the Umbraco backoffice are serialized into the rendered form and evaluated by the browser. The submission endpoint accepts field payloads without comparing them against the field configuration retrieved server side. Any control implemented purely in the client can be removed or altered by the requester before submission.

Attack Vector

The vulnerability is exploitable over the network without authentication or user interaction. An attacker crafts an HTTP POST request against the Umbraco Forms submission endpoint and includes field values that exceed the editor-configured character limits. Because no server-side check exists, the oversized values are accepted and persisted. The impact is limited to integrity of submitted form data. Confidentiality and availability are not directly affected according to the published metrics.

No public exploit code, proof of concept, or CISA KEV listing is available for this issue. See the Umbraco Forms GitHub Security Advisory GHSA-9v8m-qv22-f268 for the vendor's technical description.

Detection Methods for CVE-2025-23041

Indicators of Compromise

Stored Umbraco Forms submissions containing field values longer than the character limits configured for the corresponding short answer or long answer fields.
Web server access logs showing POST requests to Umbraco Forms submission endpoints with unusually large request bodies relative to the visible form fields.
Backoffice reports of form entries containing content that could not have been produced through the standard rendered form.

Detection Strategies

Query the Umbraco Forms submissions data store and compare each field value length against the configured maxLength for that field definition. Flag mismatches for review.
Add web application firewall rules that measure per-field payload size against expected maximums for known form endpoints.
Review recent submissions after upgrading to identify historical entries that exceeded limits prior to remediation.

Monitoring Recommendations

Log the size of each incoming form submission and alert on statistical outliers relative to baseline submissions.
Monitor changes to Umbraco Forms field configurations alongside submission patterns to detect probing.
Correlate abnormal submission sizes with source IP, user agent, and request frequency to identify automated abuse.

How to Mitigate CVE-2025-23041

Immediate Actions Required

Upgrade Umbraco Forms to 8.13.16, 10.5.7, 13.2.2, or 14.1.2 depending on the major version in use.
Inventory all Umbraco sites that use Forms and confirm the running package version through the backoffice or the .csproj package references.
Review stored submissions for oversized field content and remediate any records that violate business rules.

Patch Information

Umbraco released fixes in Umbraco Forms 8.13.16, 10.5.7, 13.2.2, and 14.1.2. The patched versions add server-side enforcement of the character limits configured on short and long answer fields. Full details are published in the Umbraco Forms GitHub Security Advisory GHSA-9v8m-qv22-f268.

Workarounds

No vendor-supplied workarounds exist. Upgrading to a fixed version is required.
As a compensating control, deploy WAF rules that reject form submissions whose field payloads exceed a conservative maximum length until patching is complete.

bash

# Configuration example: upgrade Umbraco.Forms via dotnet CLI
dotnet add package Umbraco.Forms --version 14.1.2
# For other supported branches, substitute the appropriate fixed version:
#   8.13.16, 10.5.7, or 13.2.2
dotnet restore
dotnet build