SB2021101214 - Multiple vulnerabilities in Microsoft Exchange Server

Description

This security bulletin contains information about 4 secuirty vulnerabilities.

1) Security restrictions bypass (CVE-ID: CVE-2021-26427)

The vulnerability allows a remote user to escalate privileges on the system.

The vulnerability exists due to application does not properly impose security restrictions. A remote user on the local network can send specially crafted data to the Exchange server and execute arbitrary code with elevated privileges.

2) Input validation error (CVE-ID: CVE-2021-34453)

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to insufficient validation of user-supplied input. A remote attacker can send  specially crafted input to the server and perform a denial of service (DoS) attack.

3) Security restrictions bypass (CVE-ID: CVE-2021-41348)

The vulnerability allows a remote user to escalate privileges on the system.

The vulnerability exists due to application does not properly impose security restrictions, which leads to security restrictions bypass and privilege escalation.

4) Cross-site scripting (CVE-ID: CVE-2021-41350)

The disclosed vulnerability allows a remote attacker to perform cross-site scripting (XSS) attacks.

The vulnerability exists due to insufficient sanitization of user-supplied data. A remote attacker can trick the victim to follow a specially crafted link and execute arbitrary HTML and script code in user's browser in context of vulnerable website.

Successful exploitation of this vulnerability may allow a remote attacker to steal potentially sensitive information, change appearance of the web page, perform spoofing attacks.

Remediation

Install update from vendor's website.

References

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26427
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34453
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-41348
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-41350