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Umbraco CMS Vulnerability Could Allow Privilege Escalation

by Abeerah Hashim
ConnectWise flaw risked servers

A serious vulnerability has been discovered in the Umbraco CMS, that allowed an adversary to gain admin-level privileges. Users should update the CMS to the latest version as it includes the fix.

Umbraco CMS Vulnerability

Security researchers from Trustwave have found a serious vulnerability in Umbraco CMS. Exploiting the bug could allow an adversary to gain elevated privileges on the target system.

Specifically, the vulnerability resided in an API endpoint due to improper user verification. Thus, any low privileged user could gain admin privileges.

As described in an advisory,

There is an [sic] privilege escalation issue in the core administrative screens which allow a low privileged user to access various resources otherwise limited to higher privileged users.  The issue exists in an API endpoint which does not properly check the user’s authorization prior to returning results found in the application’s logging section.

Thus, any authenticated user with low privileges could view the application logs in the core administrative screens. According to Trustwave, the risk of this information leak relied on the extent of information in the logs.

Note that the risk of the information leak will be contextualized based on what is actually logged by default or by whatever additional logging the application maintainer has decided to add.  For example, custom logging of a failed authentication routine could potentially leak usernames and passwords to the log.

Trustwave has also shared the details of this exploit in their post.

Patches Rolled Out

The researchers found the vulnerability affecting the Umbraco version 8.9.0 (also seen in 8.6.3). Whereas, Umbraco version 7.x remained unaffected by this bug.

Upon discovering this flaw in the CMS, the researchers disclosed the vulnerability to the vendors in November 2020.

Consequently, Umbraco deployed the fixes with Umbraco CMS 8.10.0 in December 2020. Though, Trustwave has clarified that they have not verified the patches.

Since the fixes are out, users must ensure updating their CMS to the latest version to avoid a potential information leak.

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