SB2026021093 - Multiple vulnerabilities in Microsoft Outlook

Description

This security bulletin contains information about 2 vulnerabilities.

1) Information disclosure (CVE-ID: CVE-2026-21260)

CWE-ID: CWE-200 - Exposure of sensitive information to an unauthorized actor

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Green

The vulnerability allows a remote attacker to gain access to potentially sensitive information.

The vulnerability exists due to excessive data output by the application in Microsoft Outlook. A remote attacker can use a specially crafted email and gain unauthorized access to sensitive information on the system.

2) Deserialization of Untrusted Data (CVE-ID: CVE-2026-21511)

CWE-ID: CWE-502 - Deserialization of Untrusted Data

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Green

The vulnerability allows a remote attacker to compromise the target system.

The vulnerability exists due to insecure input validation when processing serialized data in Microsoft Outlook. A remote attacker can pass specially crafted data to the application and gain access to sensitive information.

Remediation

Install update from vendor's website.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21260
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21511