CVE-2026-31832: Umbraco.Cms Umbraco Backoffice API Allows Unauthorized Vulnerability

MODERATE
Advisory Identifier: GHSA-fpvf-fvp5-996r
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CVSS 5.4
CWE-639
Published
Advisory Summary

CVE-2026-31832 is a MODERATE (CVSS 5.4) umbraco backoffice api allows unauthorized vulnerability (CWE-639: Authorization Bypass Through User-Controlled Key) affecting Umbraco.Cms libraries in the NuGet ecosystem. The issue involves umbraco backoffice api allows unauthorized modification of domain data. Remediation is available by upgrading affected packages to version 16.5.1, 17.2.2.

CVE-2026-31832 at a Glance

CVE Identifier CVE-2026-31832
GHSA Identifier GHSA-fpvf-fvp5-996r
Severity MODERATE
CVSS v3.1 Base Score 5.4
CWE Classification CWE-639: Authorization Bypass Through User-Controlled Key
Affected Product Umbraco.Cms
Package Ecosystem NuGet
Published Date
Last Updated

Security Impact

CVSS: 5.4

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity Low (I:L)
Availability Low (A:L)

How to Fix CVE-2026-31832

To remediate this vulnerability, upgrade all affected Umbraco.Cms dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

Umbraco.Cms fixed: 16.5.1 
Upgrade Umbraco.Cms to 16.5.1
Umbraco.Cms fixed: 17.2.2 
Upgrade Umbraco.Cms to 17.2.2
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for Umbraco.Cms

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-31832, inspect your project dependencies for Umbraco.Cms:

inspect dependencies for Umbraco.Cms

Analyze the terminal output to locate any version of Umbraco.Cms in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 16.5.1), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-639: Authorization Bypass Through User-Controlled Key, where 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. In Umbraco.Cms, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Description A broken object-level authorization vulnerability exists in a backoffice API endpoint that allows authenticated users to assign domain-related data to content nodes without proper authorization checks. The issue is caused by insufficient authorization enforcement on the affected API endpoint, whereby via an API call, domains can be set on content nodes that the editor does not have permission to access (either via user group privileges or start nodes). ### Impact An attacker can modify domain configurations for content nodes they are not permitted to edit. This may result in malicious or unintended routing behaviour, service disruption, and potential disclosure of configuration-related information. ### Patches The issue is patched in 16.5.1 and 17.2.2. ### Workarounds There is no workaround other than upgrading.

CVE-2026-31832 Affected Umbraco.Cms Versions

2 component(s)
Fixed Versions:
16.5.117.2.2
Product / Package Ecosystem Affected Versions Fixed Version
Umbraco.Cms
nuget/Umbraco.Cms
NuGet
≥ 14.0.0
< 16.5.1
16.5.1
Umbraco.Cms
nuget/Umbraco.Cms
NuGet
≥ 17.0.0
< 17.2.2
17.2.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/umbraco/Umbraco-CMS/security/advisories/GHSA-fpvf-fvp5-996r
NVD — CVE-2026-31832 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-31832
Umbraco.Cms Source Repository REPOSITORY
https://github.com/umbraco/Umbraco-CMS

Frequently Asked Questions

What is CVE-2026-31832?
CVE-2026-31832 is a security vulnerability in Umbraco.Cms involving Umbraco Backoffice API Allows Unauthorized Modification of Domain Data under CWE-639: Authorization Bypass Through User-Controlled Key.
Which Umbraco.Cms versions are affected?
Affected versions include releases prior to 16.5.1, 17.2.2 across affected packages: Umbraco.Cms.
What version fixes CVE-2026-31832?
Upgrading to 16.5.1, 17.2.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is Umbraco.Cms affected?
Yes, Umbraco.Cms is affected in releases prior to 16.5.1, 17.2.2. Upgrade your dependency to 16.5.1, 17.2.2 or later.
What is the CVSS score of CVE-2026-31832?
CVE-2026-31832 has a CVSS v3.1 base score of 5.4 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L.
What CWE is associated with CVE-2026-31832?
CVE-2026-31832 is classified under CWE-639: 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.).
How can I check NuGet dependencies for CVE-2026-31832?
Run the dependency tree command: 'inspect dependencies for Umbraco.Cms'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-fpvf-fvp5-996r",
  "modified" : "2026-03-11T05:47:21Z",
  "published" : "2026-03-11T00:24:53Z",
  "aliases" : [ "CVE-2026-31832" ],
  "summary" : "Umbraco Backoffice API Allows Unauthorized Modification of Domain Data",
  "details" : "### Description\nA broken object-level authorization vulnerability exists in a backoffice API endpoint that allows authenticated users to assign domain-related data to content nodes without proper authorization checks.\n\nThe issue is caused by insufficient authorization enforcement on the affected API endpoint, whereby via an API call, domains can be set on content nodes that the editor does not have permission to access (either via user group privileges or start nodes).\n\n### Impact\nAn attacker can modify domain configurations for content nodes they are not permitted to edit. This may result in malicious or unintended routing behaviour, service disruption, and potential disclosure of configuration-related information.\n\n### Patches\nThe issue is patched in 16.5.1 and 17.2.2.\n\n### Workarounds\nThere is no workaround other than upgrading.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Umbraco.Cms"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "14.0.0"
      }, {
        "fixed" : "16.5.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Umbraco.Cms"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "17.0.0"
      }, {
        "fixed" : "17.2.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/umbraco/Umbraco-CMS/security/advisories/GHSA-fpvf-fvp5-996r"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-31832"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/umbraco/Umbraco-CMS"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-639" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-11T00:24:53Z",
    "nvd_published_at" : "2026-03-10T22:16:21Z"
  }
}