Description

Improper authentication in Microsoft Teams allows an authorized attacker to elevate privileges over a network.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.6",
  "pubDate": "2026-08-07T00:16:36.590Z",
  "pubdate": "2026-08-07T00:16:36.590Z",
  "executiveSummary": "An improper authentication vulnerability exists within Microsoft Teams, allowing an authenticated attacker to achieve elevation of privileges across a network.\nThe flaw impacts Microsoft Teams by improperly validating authentication tokens or session states during specific communication workflows, enabling threat actors to bypass authorization boundaries.\nThe primary risk implication is unauthorized privilege escalation, which may allow malicious entities to perform actions outside their designated permission scope.\nExploitation requires network access and prior authentication to the system, meaning the attacker must already possess valid credentials or an established session within the environment.\nSuccessful exploitation grants the attacker elevated operational capabilities within the Microsoft Teams ecosystem, potentially leading to unauthorized data access, unauthorized administrative actions, or lateral movement within the application context.\nDefenders must ensure that access controls, session validation routines, and authentication enforcement mechanisms within Microsoft Teams deployments are rigorously audited and monitored.",
  "technicalDetails": "The vulnerability stems from improper authentication handling within the Microsoft Teams application architecture, specifically in how authorization checks are enforced across network-based service requests.\nThe root cause is localized to flawed trust verification logic where incoming requests fail to adequately validate whether the requesting entity possesses the necessary security context to execute privileged functionality.\nExploitation of this flaw occurs over the network, requiring the attacker to interact with vulnerable endpoints or message-handling components exposed by Microsoft Teams.\nAn attacker initiates the attack flow by authenticating normally with baseline user privileges, establishing an initial foothold within the Microsoft Teams environment.\nSubsequently, the attacker crafts and transmits manipulated requests or protocol-level payloads targeting the vulnerable component, deliberately bypassing client-side or server-side authorization checks.\nBecause the authentication subsystem improperly validates the transaction, the targeted service treats the unauthorized request as a legitimate, privileged operation.\nThis allows the payload to execute with elevated privileges, bypassing the intended security boundaries defined by the role-based access control architecture of Microsoft Teams.\nThe attack vector requires network connectivity and a valid lower-privilege account, eliminating the possibility of unauthenticated remote exploitation from the public internet without prior credentials.\nPost-exploitation impact includes the potential execution of administrative-level actions, unauthorized access to sensitive communications or resources managed by Microsoft Teams, and potential compromise of the application's underlying trust domain.\nMitigation of this technical defect requires strict enforcement of server-side authorization validations, cryptographic verification of security tokens, and comprehensive validation of all inter-process and network communications within the Microsoft Teams client-server architecture."
}