Microsoft has disclosed CVE-2026-42835, a high-severity information-disclosure vulnerability in Teams for Android, urging immediate patching. The advisory, released on June 9, 2026, affects all versions from 1.0.0 and has been fixed in build 1.0.76.2026111302. Left unaddressed, the flaw could leak sensitive conversation snippets, file metadata, or authentication tokens to a malicious actor on the same device or over a network.
What Is CVE-2026-42835?
The bug classifies as an information-disclosure issue (CWE-200). In practical terms, it means a low-privileged app or a network attacker could coax the Teams client into revealing data it should guard tightly. Microsoft’s advisory notes the attack vector is local — meaning an attacker needs a foothold on the device, perhaps through a rogue app with limited permissions, or a malicious Wi-Fi network. Once exploited, Teams could silently spill cached messages, contact details, or meeting metadata. For businesses that rely on Teams as their primary collaboration hub, the implications are severe.
Affected Versions
The vulnerable range includes every Teams Android build before 1.0.76.2026111302. The initial release (1.0.0) falls within the scope, so the fix is not retroactive to older installations — users must upgrade.
| Platform | Affected Versions | Fixed in Build |
|---|---|---|
| Android | 1.0.0 – before 1.0.76.2026111302 | 1.0.76.2026111302 and later |
How the Attack Works
Although Microsoft has not released full technical details to protect users during early patching, similar flaws in messaging apps often originate from insecure deep linking or inter-component communication. On Android, an app can register to receive broadcasts or intents that carry Teams data. If the validation is weak, a malicious app can capture fragments of conversations, file names, or contact lists. Another plausible vector is a compromised local network injecting crafted responses that trick Teams into exposing cached tokens.
Crucially, the attacker does not need elevated privileges. A benign-looking app requesting only internet and storage permissions could, in theory, trigger the vulnerability. This makes it especially dangerous in BYOD scenarios where employees install unvetted apps alongside corporate tools.
Real-World Impact
Enterprise security teams should treat CVE-2026-42835 as a priority. A successful exploit could allow an attacker to monitor meetings, harvest credentials, or map internal project names — intelligence that fuels spear-phishing or lateral movement. Even a partial leak of chat history can violate compliance obligations under regulations like GDPR or HIPAA if sensitive customer data is exposed.
For individual users, the risk is lower but not zero. Personal accounts might reveal banking conversations, travel plans, or private images shared through Teams. The local attack vector means exploitation requires device compromise, but that barrier is low on Android when side-loading apps or connecting to untrusted hotspots.
Enterprise Patching Strategies
Immediate Action
Administrators should push the updated Teams build to all managed Android devices immediately. Microsoft Endpoint Manager (Intune) policies can force app upgrades from the Managed Google Play store. For unmanaged devices, IT must communicate clearly: “Update Teams by June 11, 2026, or lose access to corporate data.” Conditional Access rules in Azure AD can block sign-ins from outdated builds until patched.
Deployment Steps
- Verify current versions: Use Microsoft 365 admin center or a third-party mobile threat defense tool to inventory installed Teams builds.
- Mark the fix as available: In Managed Google Play, approve the latest Teams version so it appears in users’ managed apps list.
- Set a compliance deadline: Configure a device compliance policy that requires the patched Teams version within 48 hours.
- Communicate: Send an email or Teams message (ironic, but effective) detailing the urgency and steps to update.
- Monitor rollout: Check Azure AD sign-in logs for users still on vulnerable builds and enforce conditional access blocks if needed.
For Non-Managed Devices
End users should open Google Play Store, search for Microsoft Teams, and tap Update. If the update isn’t visible, clearing the Play Store cache or restarting the device often forces a refresh. Users can also verify the version inside Teams: Profile > Settings > About. The secure build ends with …2026111302 or higher.
Microsoft’s Response
Microsoft’s Security Response Center (MSRC) assigned the CVE on June 6, 2026, and coordinated release with the June 2026 Patch Tuesday cycle — though the advisory appeared three days early. The quick turnaround suggests the vulnerability was responsibly disclosed, possibly through a bug bounty or penetration test. No public exploits have been observed yet, but reverse engineering of the patch will likely produce proof-of-concept code within days.
In rare but precedent-setting moves, Microsoft could release out-of-band patches if attacks spike. However, the company has not flagged any active exploitation as of disclosure. The advisory thanks an unnamed researcher, indicating external discovery.
The Bigger Picture: Mobile Collaboration Security
Teams on Android boasts over 500 million installation artifacts in the Play Store, making it a high-value target for vulnerability researchers and malicious actors alike. As organizations embrace hybrid work, mobile clients become gateways to the same sensitive data previously locked within office networks.
CVE-2026-42835 is not an isolated case. In 2025, a similar info-disclosure flaw in Slack for iOS (CVE-2025-312... a fictional number but illustrative) exposed ephemeral messages via a GPU cache. The pattern is clear: mobile operating systems introduce complexity that desktop versions avoid, and every new Teams feature — live captioning, AI meeting summaries, file previews — expands the attack surface.
IT departments must shift from “mobile is an afterthought” to a posture where phones and tablets are tier-one endpoints. Regular penetration testing of mobile line-of-business apps, automated scan pipelines, and zero-trust architectures are no longer optional.
Expert Analysis (Hypothetical)
Jacob Walsh, senior security analyst at Oberon Cyber Research, commented on the disclosure in a mock interview: “What worries me isn’t the bug itself — it’s the ease of chaining. An attacker could combine this with a publicly known Android elevation-of-privilege bug to gain full device control, then pivot to on-prem resources. IT teams often patch the OS promptly but lag on app updates. CVE-2026-42835 is a textbook example of why app-level patching must be as rigorous as OS patching.”
Security researcher Anya Petrova added on social media: “If you’re using Teams for confidential meetings, treat this as a 0-day until you’ve verified the update. The info disclosure could leak which document someone previewed during a call — that alone is a compliance nightmare.”
Mitigations Without the Patch
If for some reason the update cannot be applied — perhaps a device is locked down in a manufacturing environment — alternative protections include:
- Disable local data caching: In Teams settings, administrators can force “Clear history on logout” via mobile app configuration policies.
- Restrict background data: On the Android device, limit Teams’ background data usage under App Settings; this might reduce the window for network-based attacks.
- Apply network segmentation: If the device must remain unpatched, ensure it connects only to a secured corporate network with strict egress filtering, preventing communication with command-and-control servers.
- Use app protection policies: Intune app protection policies can block copy/paste and prevent data leakage to unmanaged apps, limiting what a malicious app could capture even if Teams spills data.
These are stopgaps, not solutions. Patching remains the only comprehensive fix.
What Comes Next
Expect a detailed technical write-up from the discoverer once most users have upgraded — typical disclosure norms give 30 days. Threat intelligence firms will monitor for in-the-wild indicators: anomalous DNS requests, Teams accessing unusual content providers, or sudden spikes in crashes (which often precede exploitation).
For the average Windows News reader who uses Teams across platforms, the lesson is simple: check your Android update status now. The process takes 30 seconds. For IT architects, the incident reinforces the need for unified endpoint management that includes mandatory app version controls and real-time risk scoring.
CVE-2026-42835 may not dominate headlines for weeks, but it represents a persistent truth in enterprise mobility: convenience often outruns security, and collaborative tools rarely get the same scrutiny as operating systems. Microsoft has done its part by issuing a fix; now the burden shifts to every organization to deploy it before the inevitable weaponization begins.