CVE-2026-42835: Microsoft Teams for Android Injection Vulnerability Allows Information Disclosure

Technical summary

CVE-2026-42835 is an injection vulnerability (CWE-74) in Microsoft Teams for Android that fails to neutralize special elements before passing data to downstream components. The vulnerability has a CVSS v3.1 score of 8.1 (HIGH), with a network attack vector, low attack complexity, and requirement for low-level privileges (authenticated user). The impact is confined to confidentiality (HIGH) and availability (HIGH), with no integrity compromise. The attack requires no user interaction, making it feasible in enterprise environments where Teams is widely deployed on employee Android devices.

Business impact

This vulnerability poses a significant risk to organizations using Microsoft Teams on Android devices, particularly those handling sensitive information through the platform. Authenticated users—whether internal employees or external collaborators—can potentially extract confidential data including messages, files, or metadata without detection. For enterprises with BYOD policies or contractor access, the low barrier to exploitation (authentication only) increases exposure. The HIGH impact on confidentiality combined with availability concerns suggests potential for service disruption or data exfiltration campaigns.

Affected systems

Microsoft Teams for Android is the sole affected product identified in this CVE. Organizations must assess the scale of Android Teams deployment in their environment, including personal devices, shared devices, and corporate-managed fleet. The vulnerability affects all versions of Teams for Android until patching; however, specific affected version ranges have not been disclosed in available advisories—consult Microsoft's official security bulletin for precise version boundaries.

Exploitability

The vulnerability requires an authenticated user context, reducing the pool of potential attackers to those with valid Teams credentials. However, low attack complexity and absence of user interaction requirements mean exploitation can be automated once access is obtained. The network-based attack vector allows remote exploitation without physical access. Given the widespread distribution of Teams for Android and the commonplace nature of user credentials, exploitability is moderate to high for motivated threat actors, though mass exploitation is less likely than targeted attacks against high-value users or organizations.

Remediation

Organizations should prioritize patching Microsoft Teams for Android across all managed and unmanaged devices. Implement Mobile Device Management (MDM) policies to enforce application updates automatically or block outdated versions from accessing corporate resources. For BYOD environments, communicate patch availability to users and consider compliance requirements tied to app currency. In the interim, restrict Teams on Android to less-critical workflows and monitor authentication logs for unusual access patterns. Verify patch status against Microsoft's official advisory to confirm version numbers addressing this specific vulnerability.

Patch guidance

Contact Microsoft Security Updates or consult the official Teams security advisories for patched version numbers and deployment timelines. Organizations using Microsoft Endpoint Manager or Intune can deploy patches through centralized update policies. For personal devices, ensure Teams auto-update is enabled in the Google Play Store. Test patches in a limited deployment before organization-wide rollout to confirm functionality. Patch deployment should prioritize devices with access to sensitive information or critical collaboration workflows.

Detection guidance

Monitor for anomalous data access patterns in Teams, particularly extraction or export of messages and files by authenticated users. Detect unusual authentication from Android clients, especially from unfamiliar devices or geographic locations. Review audit logs in Microsoft 365 for high-volume content access or unusual export activities correlated with Teams for Android sessions. Look for unexpected availability degradation or service errors that could indicate exploitation-related crashes. Network-based detection is limited due to encrypted traffic, but endpoint and identity monitoring can flag suspicious behavioral patterns.

Why prioritize this

Despite requiring authentication, the HIGH CVSS score (8.1) reflects substantial confidentiality and availability impact. The network attack vector and low complexity make this a priority for patching in mobile-first enterprises. Android's fragmented update landscape and the ubiquity of Teams in corporate communications justify rapid remediation. Organizations should prioritize this above low-complexity vulnerabilities with identical or lower CVSS scores.

Risk score, explained

The CVSS 3.1 score of 8.1 (HIGH) reflects a network-accessible vulnerability with low attack complexity that compromises confidentiality and availability for authenticated users. The requirement for prior authentication (PR:L) prevents a maximum score, but the lack of user interaction (UI:N) and broad scope of data at risk elevate severity. The HIGH confidentiality impact dominates the score, reflecting the core threat of information disclosure. Organizations with high-value data in Teams should treat this as critical despite the authentication requirement.

Frequently asked questions