CVE-2026-42835 Overview
CVE-2026-42835 is an injection vulnerability in Microsoft Teams for Android. The flaw stems from improper neutralization of special elements passed to a downstream component [CWE-74]. An authorized attacker can exploit the issue over a network to disclose information from the affected application.
Microsoft published the advisory on June 9, 2026. The vulnerability requires low privileges and no user interaction. It affects confidentiality and availability of the Teams Android client.
Critical Impact
An authenticated remote attacker can inject crafted input that propagates to a downstream component, leading to unauthorized disclosure of sensitive information and potential disruption of the Teams for Android client.
Affected Products
- Microsoft Teams for Android
- Mobile collaboration deployments dependent on the Teams Android client
- Enterprise environments using Microsoft 365 with Teams mobile access
Discovery Timeline
- 2026-06-09 - CVE-2026-42835 published to NVD
- 2026-06-09 - Last updated in NVD database
Technical Details for CVE-2026-42835
Vulnerability Analysis
The vulnerability is classified under [CWE-74], improper neutralization of special elements in output used by a downstream component. Microsoft Teams for Android fails to sanitize attacker-controlled input before it reaches an internal handler. The downstream component interprets the unsanitized data, allowing the attacker to influence its behavior.
Exploitation requires the attacker to hold valid credentials or an authenticated session within the Teams environment. The attack traverses the network and does not require interaction from the victim. A successful attack results in disclosure of sensitive data and can impair service availability on the affected client.
Root Cause
The root cause is missing or insufficient input neutralization at a trust boundary inside the Teams for Android application. Special characters or structured payloads that should be escaped, encoded, or rejected are forwarded to a downstream parser or interpreter. The downstream component then treats portions of the input as control data rather than literal content, producing unintended actions.
Attack Vector
The attack vector is network-based. An authenticated attacker sends a crafted message, request, or shared resource through Teams services that is rendered or processed by a victim instance of Teams for Android. The injected payload triggers the downstream component to leak data that the attacker would not otherwise be authorized to read. Refer to the Microsoft CVE-2026-42835 Advisory for vendor technical detail.
No public proof-of-concept code is available at the time of publication, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. The EPSS probability stands at 0.163%.
Detection Methods for CVE-2026-42835
Indicators of Compromise
- Anomalous Teams messages or chat payloads containing unusual control characters, escape sequences, or structured markup directed at Android clients.
- Unexpected outbound network connections from the Teams for Android process to unfamiliar endpoints following message receipt.
- Mobile device logs showing repeated parsing errors or crashes in the Teams application correlated with inbound messages from a single sender.
Detection Strategies
- Inspect Teams audit logs for messages and shared content originating from low-privilege accounts that contain malformed or injected payloads.
- Correlate authentication events with subsequent abnormal Teams API requests from the same identity targeting mobile sessions.
- Apply behavioral monitoring on Android endpoints to flag Teams client behavior that deviates from baseline, including unexpected data egress.
Monitoring Recommendations
- Centralize Microsoft 365 audit logs and Teams message-trace telemetry for retroactive search of injection patterns.
- Monitor mobile device management (MDM) inventory to confirm Teams for Android versions remain current across the fleet.
- Alert on Teams accounts exhibiting bulk-messaging behavior toward internal users, which can precede targeted injection attempts.
How to Mitigate CVE-2026-42835
Immediate Actions Required
- Update Microsoft Teams for Android to the fixed version distributed through Google Play as referenced in the Microsoft CVE-2026-42835 Advisory.
- Enforce automatic application updates through MDM policies to ensure all managed Android devices receive the patch.
- Review Teams tenant access for unused or over-privileged accounts and remove unnecessary authenticated identities.
Patch Information
Microsoft has released an updated Teams for Android client that addresses the improper neutralization issue. Apply the vendor-supplied update through the Google Play Store or enterprise mobile distribution channels. Consult the official advisory for version-specific guidance.
Workarounds
- Restrict Teams external federation and guest access until all Android clients are updated, reducing the population of potential authenticated attackers.
- Apply conditional access policies that block outdated Teams for Android client versions from connecting to the tenant.
- Educate users to report unexpected messages containing unusual formatting or links, and to keep mobile applications updated.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
