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Privacy Statement Third-Party Cookies AcceptRejectManage cookies MSRC  Customer Guidance  Security Update Guide  Vulnerabilities  CVE-2026-55007 Microsoft Exchange Server Remote Code Execution Vulnerability New On this page  CVE-2026-55007  Subscribe RSS PowerShell  API  CSAF Security Vulnerability Released: Sep 8, 2026 Assigning CNA Microsoft CVE.org link CVE-2026-55007  Impact Remote Code Execution Max Severity Important Weakness CWE-415: Double Free CVSS Source Microsoft Vector String CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C Metrics CVSS:3.1 8.1 / 7.1  Base score metrics: 8.1 / Temporal score metrics: 7.1  Expand all  Collapse all Metric Value   Base score metrics(8) Attack Vector Network Attack Complexity High Privileges Required None User Interaction None Scope Unchanged Confidentiality High Integrity High Availability High   Temporal score metrics(3) Exploit Code Maturity Unproven Remediation Level Official Fix Report Confidence Confirmed Please see Common Vulnerability Scoring System for more information on the definition of these metrics. Executive Summary Double free in Microsoft Exchange Server allows an unauthorized attacker to execute code over a network. Exploitability The following table provides an exploitability assessment for this vulnerability at the time of original publication. Publicly disclosed No Exploited No Exploitability assessment Exploitation Less Likely FAQ How could an attacker exploit this vulnerability? An unauthenticated attacker could send a specially crafted Visio attachment to an affected Exchange server. The server could process the attachment during content indexing, and successful exploitation could allow the attacker to execute code on the server. User interaction is not required. According to the CVSS metric, the attack complexity is high (AC:H). What does that mean for this vulnerability? Successful exploitation requires the target system to be under sustained low-memory (memory pressure) conditions, which are not commonly present in normal operation. This makes the vulnerability difficult to reliably trigger, as the attacker must first induce or wait for a constrained memory state before exploitation becomes possible. Acknowledgements Anonymous Microsoft recognizes the efforts of those in the security community who help us protect customers through coordinated vulnerability disclosure. See Acknowledgements for more information. Security Updates To determine the support lifecycle for your software, see the Microsoft Support Lifecycle. Release date Descending  Edit columns  Download  Filters  Product Family  Max Severity  Impact  Platform   Clear Release date  Product Platform Impact Max Severity Article Download Build Number Assigning CNA Title: Release date, Content: Sep 8, 2026 Microsoft Exchange Server Subscription Edition RTM - Remote Code Execution Important Title: Knowledge Base Articles for Microsoft Exchange Server Subscription Edition RTM, Content:, 1 link 5121608  Title: Download Security Update for Microsoft Exchange Server Subscription Edition RTM, Content:, 1 link Security Update  Title: Build numbers, Content: 15.02.2562.049 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Sep 8, 2026 Microsoft Exchange Server 2019 Cumulative Update 15 - Remote Code Execution Important Title: Knowledge Base Articles for Microsoft Exchange Server 2019 Cumulative Update 15, Content:, 1 link 5121609  Title: Download Security Update for Microsoft Exchange Server 2019 Cumulative Update 15, Content:, 1 link Security Update Title: Build numbers, Content: 15.02.1748.051 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Sep 8, 2026 Microsoft Exchange Server 2019 Cumulative Update 14 - Remote Code Execution Important Title: Knowledge Base Articles for Microsoft Exchange Server 2019 Cumulative Update 14, Content:, 1 link 5121610  Title: Download Security Update for Microsoft Exchange Server 2019 Cumulative Update 14, Content:, 1 link Security Update Title: Build numbers, Content: 15.02.1544.046 Title: Assigning CNA, Content: Microsoft All results loaded Loaded all 3 rows Disclaimer The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply. Revisions version revisionDate description 1.0 Sep 8, 2026 Information published.  How satisfied are you with the MSRC Security Update Guide? Rating  Broken  Bad  Below average  Average  Great!  Your Privacy Choices Consumer Health Privacy Privacy & Cookies