Microsoft has disclosed a high-severity information disclosure vulnerability in Microsoft Teams for Android, tracked as CVE-2026-42835, as part of its June 2026 Patch Tuesday updates. The vulnerability, made public on June 9, 2026, allows an authorized attacker to disclose sensitive information over a network, posing significant risks to enterprise and individual users alike. While Microsoft has not released full technical specifics, the classification as "high severity" and the nature of the flaw demand immediate attention from IT administrators and Android device users.

Understanding CVE-2026-42835

CVE-2026-42835 affects the Android version of Microsoft Teams, the widely used collaboration platform. The vulnerability is categorized as an information disclosure issue, meaning that an attacker who successfully exploits it could gain access to information that they should not be able to view. Microsoft's advisory, though sparse, indicates that the attack vector is network-based, with low attack complexity and no user interaction required. The vector string provided in the advisory suggests that exploitation is possible over a network without any prior privileges, though the attacker must be "authorized" in some context—likely meaning they need to be authenticated to the Teams environment or have some level of access before they can leverage the flaw.

Information disclosure vulnerabilities in mobile apps can have severe repercussions. In the context of Teams for Android, sensitive data could include chat messages, meeting notes, shared files, user profile details, or authentication tokens. Given that Teams often handles confidential business communications and integrates with other Microsoft 365 services, any leak could facilitate further attacks such as phishing, account takeover, or lateral movement within an organization.

CVSS Score and Severity

The Common Vulnerability Scoring System (CVSS) v3.1 base score for CVE-2026-42835 has been assessed at 7.5 out of 10, placing it firmly in the "High" severity band. A breakdown of the vector (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N) reveals:

  • Attack Vector (AV): Network (N) – Exploitable remotely.
  • Attack Complexity (AC): Low (L) – No special conditions required.
  • Privileges Required (PR): None (N) – Attacker does not need any privileges.
  • User Interaction (UI): None (N) – Victim does not need to click or perform any action.
  • Scope (S): Unchanged (U) – The vulnerable component and the impacted component are the same.
  • Confidentiality Impact (C): High (H) – Total information disclosure.
  • Integrity Impact (I): None (N) – No alteration of data.
  • Availability Impact (A): None (N) – No disruption of service.

This scoring indicates that the vulnerability is trivial to exploit and leads to a complete loss of confidentiality, but does not affect data integrity or system availability. The lack of required privileges and user interaction makes it particularly dangerous, as automated tools could scan for vulnerable versions and extract data en masse.

Affected Versions

Microsoft has not publicly listed the specific version numbers of Teams for Android that are affected. Typically, the advisory would include a table of affected and fixed versions, but at the time of disclosure, Microsoft advised that the security update is available through the Google Play Store. Users are urged to ensure their Teams app is updated to the latest version, which contains the patch. It is standard practice for Microsoft to assign a single CVE to cover a range of affected builds, and the fix is delivered via a regular app update rather than an OS-level patch.

Based on Microsoft's standard lifecycle, the Teams Android app receives frequent updates. The vulnerability was likely introduced in a recent version and resolved in a subsequent release. Administrators managing corporate devices via Microsoft Intune or other MDM solutions should push the latest version immediately.

Technical Implications and Attack Scenarios

While the exact nature of the flaw remains undisclosed to prevent exploitation before all users have updated, information disclosure vulnerabilities in messaging apps often stem from:

  • Improper handling of intents or deep links that expose internal data to other apps.
  • Insecure storage of cache, logs, or session tokens.
  • Flaws in the handling of WebView content that allow JavaScript injection or data leakage.
  • Exposed content providers that can be queried by other malicious apps on the same device.
  • Network communication issues such as missing certificate pinning or improper TLS configuration, allowing man-in-the-middle attacks.

Given that the CVSS vector indicates no privileges are required, it is plausible that an attacker could exploit this without being authenticated to Teams. In an enterprise setting, this could mean a malicious app on a co-worker's device, a compromised network device, or an attacker on the same public Wi-Fi network. The scope being unchanged suggests the vulnerability does not break out of the app's sandbox into the OS, but still exposes app-specific data.

Mitigation and Patching

There are no viable workarounds for CVE-2026-42835 according to Microsoft; the only effective mitigation is to apply the update. Users should:

  1. Open the Google Play Store, navigate to "My apps & games," and update Microsoft Teams if an update is available.
  2. Enable automatic updates for the Teams app to prevent future delays.
  3. Verify the app version after update: while Microsoft has not published a fixed version number, any build dated June 2026 or later should contain the patch.
  4. For enterprise deployments, use Microsoft Endpoint Manager (Intune) to force an update on managed devices.
  5. Review conditional access policies to block access from outdated app versions, though this is a temporary stopgap.

Organizations should also monitor their Microsoft 365 security dashboards and any third-party mobile threat detection solutions for signs of exploitation. While no active exploits have been reported in the wild at the time of disclosure, the low attack complexity makes it a prime target for inclusion in automated attack toolkits.

Microsoft's Response and Patch Tuesday Context

June 9, 2026, falls on the second Tuesday of the month, aligning with Microsoft's scheduled Patch Tuesday. This release addressed dozens of vulnerabilities across Microsoft products. CVE-2026-42835 is one of several mobile-related flaws patched this month. Microsoft's Security Response Center (MSRC) typically assigns CVE IDs like this when the vulnerability is reported responsibly or discovered internally.

The advisory for CVE-2026-42835 notes that the flaw was privately reported and there is no evidence of public disclosure or active exploitation prior to the patch. Microsoft's decision to withhold detailed technical information is consistent with their standard practice for newly patched vulnerabilities, giving users time to update before threats incorporate the exploit.

Historical Context: Microsoft Teams Security

Microsoft Teams has been subject to several critical vulnerabilities in the past. In 2020, a GIF-based subdomain takeover allowed account compromise. In 2023, a flaw in the Teams desktop client allowed external attackers to send malicious messages and access internal networks. The shift to mobile platforms has expanded the attack surface, making Android and iOS apps regular targets. For Android specifically, the fragmented ecosystem and delayed OS updates compound the risk when app-level vulnerabilities arise. CVE-2026-42835 underscores the importance of keeping collaboration apps updated across all devices, especially in bring-your-own-device (BYOD) scenarios.

Recommendations for End Users and IT Administrators

  • Update immediately: Check the Play Store or your enterprise app store for the latest Teams version.
  • Review app permissions: On Android, verify that Teams does not have unnecessary permissions that could be abused in conjunction with this vulnerability.
  • Educate users: Remind employees not to sideload APKs or click on suspicious links that could install malicious apps aiming to exploit this flaw through inter-app communication.
  • Enable mobile threat defense: Use solutions like Microsoft Defender for Endpoint on Android to detect anomalous behavior.
  • Monitor Microsoft 365 audit logs: Look for unusual access patterns or data exports from Teams that may indicate successful exploitation.
  • Apply zero trust principles: Assume breach and limit the sensitivity of data shared via Teams where possible. Use data loss prevention (DLP) policies to block sensitive information from being improperly shared.

Future Outlook and Patch Management Maturity

The discovery of CVE-2026-42835 highlights the ongoing challenges in securing mobile collaboration tools. As remote work remains a staple, Teams for Android is a critical endpoint that must be managed with the same rigor as desktop clients. Microsoft’s prompt patching on Patch Tuesday demonstrates a mature security response, but the responsibility shifts to users and admins to apply the update. Moving forward, automated update enforcement and runtime application self-protection (RASP) may reduce the window of exposure for such vulnerabilities.

Microsoft has not indicated whether this CVE will lead to any changes in their mobile development lifecycle or security testing practices. However, given the high severity and the ease of exploitation, it may trigger a deeper review of the Teams Android codebase. For now, the immediate action is clear: update Microsoft Teams for Android to the latest version as soon as possible to protect against potential information disclosure attacks.