VulnerabilityPublished 10 Mar 2026

CVE-2026-31832: Umbraco-CMS · Insecure Direct Object Reference

Affects Umbraco-CMSSource CVE Database V5

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Not known to be exploited · CVSS 5.4 Medium : upgrade to 17.2.0 or 16.5.1 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

5.4Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 17.2.0, 16.5.1, 17.2.2

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 10 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Umbraco-CMS to 17.2.0 or 16.5.1; umbraco/umbraco-cms to 17.2.2 or 16.5.1.

Affected software

Product	Affected	Fixed in
umbracoUmbraco-CMS	Affected >=17.0.0 <17.2.0	Fixed in 17.2.0
umbracoUmbraco-CMS	Affected >=14.0.0 <16.5.1	Fixed in 16.5.1
NuGetumbraco/umbraco-cms`pkg:nuget/umbraco/umbraco-cms`Other threats	Affected >=14.0.0 <16.5.1 >=17.0.0 <17.2.2	Fixed in 16.5.1 17.2.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Organizations should upgrade affected Umbraco CMS instances to version 16.5.1 or 17.2.2 or later, where the vulnerability is patched. Until upgrades can be applied, administrators should restrict access to the backoffice API endpoints to trusted users only and review user group permissions to minimize the number of users with domain assignment privileges. Implementing strong authentication mechanisms, such as multi-factor authentication (MFA), can reduce the risk of compromised accounts being used to exploit this flaw. Regularly audit content node permissions and domain assignments to detect unauthorized changes promptly. Additionally, monitoring API access logs for unusual activity related to domain assignments can help identify exploitation attempts. Employing web application firewalls (WAFs) with custom rules to detect anomalous API calls may provide temporary mitigation. Finally, ensure that all CMS users are trained on security best practices to prevent credential misuse.

Description

Umbraco is an ASP.NET CMS. From 14.0.0 to before 16.5.1 and 17.2.2, 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). This vulnerability is fixed in 16.5.1 and 17.2.2.

Impact

The primary impact of this vulnerability is unauthorized modification of domain assignments on content nodes within Umbraco CMS-managed websites. This can lead to integrity issues where content or domain configurations are altered without proper authorization, potentially causing website misconfigurations, content misrouting, or service disruptions. Although confidentiality is not directly impacted, the integrity and availability of website content can be compromised, which may affect user trust and business operations. Organizations relying on Umbraco CMS for critical web content management could face reputational damage, operational downtime, or increased administrative overhead to detect and remediate unauthorized changes. Since exploitation requires only authenticated access, insider threats or compromised user accounts increase the risk. The vulnerability does not appear to have known exploits in the wild yet, but the medium severity and ease of exploitation warrant prompt attention.

CWE-639Authorization Bypass Through User-Controlled Key (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #24OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
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.
Architecture and Design
For each and every data access, ensure that the user has sufficient privilege to access the record that is being requested.
Architecture and Design · Implementation
Make sure that the key that is used in the lookup of a specific user's record is not controllable externally by the user or that any tampering can be detected.
Architecture and Design
Use encryption in order to make it more difficult to guess other legitimate values of the key or associate a digital signature with the key so that the server can verify that there has been no tampering.
OWASP Cheat Sheets
Access Control (opens in a new tab)
Authorization Testing Automation (opens in a new tab)
Cross-Site Request Forgery Prevention (opens in a new tab)
Insecure Direct Object Reference Prevention (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V4.1.2 (opens in a new tab)
V4.2.1 (opens in a new tab)
V8.3.8 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

github.com/umbraco/Umbraco-CMS/security/advisories/GHSA-fpvf-fvp5-996r (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 10 Mar 2026, 22:14 UTC

WeaknessesCWE-639

Technical details

References

Community reviews

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