CVE-2026-62918 in Teams
Summary
by MITRE • 08/07/2026
Improper verification of cryptographic signature in Microsoft Teams allows an unauthorized attacker to perform spoofing over a network.
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Analysis
by VulDB Data Team • 08/07/2026
This vulnerability represents a critical failure in the cryptographic signature verification process within Microsoft Teams, specifically affecting the integrity validation mechanisms that protect against unauthorized message manipulation and impersonation attacks. The flaw resides in how the application validates digital signatures associated with communications, potentially allowing attackers to forge legitimate-looking messages or alter existing communications without detection. This weakness directly impacts the security posture of Microsoft Teams deployments by undermining the fundamental trust model that should prevent malicious actors from masquerading as authorized users or modifying sensitive information during transmission.
The technical implementation of this vulnerability stems from insufficient validation of cryptographic signatures, which typically would require verification against established public key infrastructure standards and proper certificate chain validation. Attackers exploiting this flaw could potentially construct malicious communications that appear authentic to recipients, leveraging the trust relationships inherent in the Teams ecosystem to bypass normal security controls. This represents a classic case of inadequate input validation and cryptographic integrity checking, aligning with common weakness patterns identified in CWE-347 for insufficient verification of cryptographic signatures and CWE-295 for improper certificate validation. The vulnerability may affect various communication channels within Teams including chat messages, file transfers, and collaborative document editing features where cryptographic signatures are expected to maintain data integrity.
Operationally, this vulnerability creates significant risk for organizations relying on Microsoft Teams for secure communications, as it enables sophisticated social engineering attacks where malicious actors can craft convincing impersonation scenarios. The impact extends beyond simple message spoofing to potentially compromise sensitive business communications, collaboration workflows, and confidential information exchanges between team members and external partners. Organizations may experience unauthorized access to privileged information, disruption of legitimate business processes, and potential data exfiltration through manipulated communications that appear legitimate to end users. This vulnerability particularly affects environments where Teams serves as the primary communication platform for sensitive corporate activities, making it a prime target for advanced persistent threat actors seeking to establish long-term presence within network perimeters.
Mitigation strategies should focus on immediate implementation of Microsoft security updates and patches addressing the cryptographic signature verification weakness, along with enhanced monitoring of suspicious communications patterns within Teams environments. Organizations should consider implementing additional security controls such as message encryption overlays, enhanced user authentication mechanisms, and regular security assessments of collaboration platforms to detect potential exploitation attempts. Network segmentation and access controls should be reviewed to limit the blast radius of potential exploitation, while security awareness training should emphasize recognizing signs of impersonation attacks that may leverage this vulnerability. The remediation process should align with established cybersecurity frameworks such as the mitre ATT&CK framework's technique T1566 for credential harvesting through social engineering, ensuring comprehensive defense-in-depth strategies are implemented to address both the immediate vulnerability and broader threat landscape surrounding collaborative platforms.