SB2026090908 - Multiple vulnerabilities in Microsoft Exchange Server

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Main Vulnerability Database SB2026090908

SB2026090908 - Multiple vulnerabilities in Microsoft Exchange Server

Published: September 9, 2026

Security Bulletin ID SB2026090908
CSH Severity
High
Patch available
YES
Number of vulnerabilities 9
Exploitation vector Remote access
Highest impact Code execution

Breakdown by Severity

High 11% Medium 56% Low 33%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 9 vulnerabilities.


1) Double free (CVE-ID: CVE-2026-55007)

CWE-ID: CWE-415 - Double Free

CVSSv4: 9.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]


The vulnerability allows a remote attacker to execute arbitrary code.

The vulnerability exists due to a double free in Microsoft Exchange Server when processing a specially crafted Visio attachment during content indexing. A remote attacker can send a specially crafted Visio attachment to an affected Exchange server to execute arbitrary code.

Successful exploitation requires the target system to be under sustained low-memory conditions.


2) External Control of File Name or Path (CVE-ID: CVE-2026-69355)

CWE-ID: CWE-73 - External Control of File Name or Path

CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]


The vulnerability allows a remote user to execute arbitrary code.

The vulnerability exists due to external control of file name or path in Microsoft Exchange Server when handling a specially crafted request. A remote user can send a specially crafted request to execute arbitrary code.

User interaction is not required.


3) Cross-site scripting (CVE-ID: CVE-2026-69356)

CWE-ID: CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSSv4: 5.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N]


The vulnerability allows a remote attacker to perform spoofing.

The vulnerability exists due to improper neutralization of input during web page generation (cross-site scripting) in Microsoft Exchange Server when processing a specially crafted calendar invitation containing a malicious meeting link. A remote attacker can send a specially crafted calendar invitation to perform spoofing.

User interaction is required to open the meeting and select the Join link.


4) Server-Side Request Forgery (SSRF) (CVE-ID: CVE-2026-69361)

CWE-ID: CWE-918 - Server-Side Request Forgery (SSRF)

CVSSv4: 7.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]


The vulnerability allows a remote user to disclose sensitive information.

The vulnerability exists due to server-side request forgery (ssrf) in Microsoft Exchange Server when processing a specially crafted internet calendar subscription. A remote user can submit a specially crafted internet calendar subscription to disclose sensitive information.

The affected server can be induced to send HTTP requests to internal or loopback systems.


5) Authorization bypass through user-controlled key (CVE-ID: CVE-2026-69375)

CWE-ID: CWE-639 - Authorization Bypass Through User-Controlled Key

CVSSv4: 7.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]


The vulnerability allows a remote user to tamper with file content.

The vulnerability exists due to authorization bypass through a user-controlled key in Microsoft Exchange Server when handling network requests. A remote user can replace valid file content with specially crafted file content to tamper with file content.


6) Uncontrolled Recursion (CVE-ID: CVE-2026-69378)

CWE-ID: CWE-674 - Uncontrolled Recursion

CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]


The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to uncontrolled recursion in Microsoft Exchange Server when processing network requests. A remote attacker can send network requests that trigger uncontrolled recursion to cause a denial of service.


7) Missing Authorization (CVE-ID: CVE-2026-69380)

CWE-ID: CWE-862 - Missing Authorization

CVSSv4: 8.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N]


The vulnerability allows a remote user to elevate privileges.

The vulnerability exists due to missing authorization in Microsoft Exchange Server when validating requests and identity tokens. A remote user can impersonate another user to elevate privileges.

Exploitation requires a low-privilege user account with an assigned mailbox.


8) Use of a broken or risky cryptographic algorithm (CVE-ID: CVE-2026-69382)

CWE-ID: CWE-327 - Use of a Broken or Risky Cryptographic Algorithm

CVSSv4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]


The vulnerability allows a remote attacker to disclose credentials.

The vulnerability exists due to use of a broken or risky cryptographic algorithm in Microsoft Exchange Server when processing repeated requests using a valid encrypted authentication cookie. A remote attacker can make repeated requests to infer protected credentials to disclose credentials.


9) Missing Authorization (CVE-ID: CVE-2026-69641)

CWE-ID: CWE-862 - Missing Authorization

CVSSv4: 8.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]


The vulnerability allows a remote user to access or modify other users\' mailbox content.

The vulnerability exists due to missing authorization in Microsoft Exchange Server when processing specially crafted network requests. A remote privileged user can send a specially crafted request to bypass mailbox authorization checks and access or modify other users\' mailbox content.

No user interaction is required.


Remediation

Install update from vendor's website.

References