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A high-severity vulnerability in Microsoft Authenticator for Android could let a malicious app, without any Android permissions, impersonate trusted Microsoft apps and steal authentication tokens for a victim’s signed-in work account.

This vulnerability is tracked as CVE-2026-80097 and affects Microsoft Authenticator versions earlier than 6.2606.4246. Microsoft has since issued a patch.

Security researchers at Enclave discovered that the problem originated from an exported Android activity called com.microsoft.identity.client.AccountChooserActivity.

Because this activity was accessible from outside the app, another app on the device could launch it and request tokens through Authenticator’s broker service.

The vulnerable workflow trusted identity details supplied by the requesting app, which included the claimed package name, client ID, redirect URI, scopes, and even the caller’s UID.

While Authenticator did perform a redirect-URI validation check, it merely verified the signature-derived redirect URI for the claimed app package instead of confirming that the real calling application matched that package.

This oversight meant that an attacker could masquerade as an installed Microsoft application, such as Microsoft Teams. They could construct the expected redirect URI from the legitimate app’s installed signature and pass validation.

Research showed that while Authenticator could identify the real caller through Android’s getCallingActivity() mechanism, it did not use this information in its security decisions.

Once the request was accepted, Authenticator would return token data to the requesting app via the activity result. According to the researchers, this returned broker response could contain access tokens, refresh tokens, ID tokens, and client information in plaintext, enabling the malicious app to parse and reuse them.

In testing,impersonating Microsoft Teamswhile requesting access to Microsoft Graph resulted in delegated permissions that could allow mailbox, calendar, file, SharePoint, and chat-related actions.

The researchers also demonstrated that token issuance could occur while impersonating a Teams backend client and Authenticator’s own client identity, each with different permission scopes.

Microsoft classified CVE-2026-80097 as an elevation-of-privilege vulnerability, assigning it a CVSS score of 8.6 and mapping it to CWE-287, Improper Authentication. Microsoft has confirmed the report, issued a fix, and published the vulnerability advisory on September 8, 2026.

Organizations using Microsoft Authenticator on Android should ensure that their deployed devices are running version 6.2606.4246 or later. Mobile threat detection teams should also monitor managed Android devices for unexpected token use, suspicious Microsoft Graph activity, and unauthorized application behavior on managed Android devices.

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