Microsoft Exchange Server Spoofing Vulnerability
Published July 14, 2026Updated July 14, 2026
Source data
Overview
Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.
Impact & technical details
Spoofing
Microsoft recommends installing the July 2026 Security Updates for your version of Exchange Server to be protected from this vulnerability. Customers who have installed the July 2026 Security Updates on all affected Exchange servers are fully protected and may safely remove the CVE-2026-42897 mitigation (which is similar in nature and mitigates CVE-2026-55008 also). Microsoft recommends keeping the Emergency Mitigation (EM) Service enabled to receive future emergency mitigations and security protections. For additional information, please see the Exchange blog post .
How could an attacker exploit this vulnerability? An attacker could exploit this issue by sending a specifically crafted malicious email to the user. If the user opens this email, in Outlook Web Access, and certain conditions are met, arbitrary execution of JavaScript would occur in the browser context.
- CVSS base score
- 9.6 / 10
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C
Highest base score supplied by MSRC for this record; the vector belongs to that score. Ratings can vary by product. Microsoft Important is displayed as High; Moderate is displayed as Medium.
Affected products
- Microsoft Exchange Server 2016 Cumulative Update 23
- Microsoft Exchange Server 2019 Cumulative Update 14
- Microsoft Exchange Server 2019 Cumulative Update 15
- Microsoft Exchange Server Subscription Edition RTM
Source guidance
Remediation
The source provides update references without a separate remediation summary. Review the applicable update links below.
At least one Microsoft vendor-fix reference is available. Check each affected product for its applicable update, prerequisites, and supported version.
GTP recommendation · Rule-based guidance
Recommended next step
Review affected systems and prioritize deployment of the vendor security update.
Authoritative sources & updates
Findings and update information come from the linked publishers. GTP compiles the public record and provides the recommendation above. CVSS ratings shown here come from Microsoft. NVD references provide additional public context.
- Microsoft Security Response Center (opens in a new tab)
- Microsoft remediation guidance (opens in a new tab)
- Microsoft remediation guidance (opens in a new tab)
- Microsoft remediation guidance (opens in a new tab)
- Microsoft security update · 5103212 (opens in a new tab)
- Microsoft remediation guidance (opens in a new tab)
Managed by GTP?
Griffin Technology Partners managed customers may receive additional environment-specific security guidance and remediation assistance through their managed services relationship.
Security bulletins are provided for informational purposes and compiled from authoritative public sources. Vulnerability applicability varies by environment. Validate affected products, configuration, compatibility requirements, and vendor guidance before making production changes.