[Update] Vulnerability in Microsoft Exchange Server (May 15, 2026)
Actively exploited. At least one CVE in this advisory is listed in the CISA Known Exploited Vulnerabilities catalog — exploitation has been observed in the wild. Treat remediation as urgent.
[Update on June 11, 2026] On June 9, 2026, Microsoft released corrective versions. [Initial publication] On May 14, 2026, Microsoft published a security notice regarding the vulnerability CVE-2026-42897 affecting Exchange Server. It allows an unauthenticated attacker to cause...
CSIRTS triage
- What
- A vulnerability in Microsoft Exchange Server allows an unauthenticated attacker to exploit the system.
- Who is affected
- Users of Microsoft Exchange Server are affected.
- Urgency
- Remediation is urgent due to the critical nature of the vulnerability and its exploitation status.
- Action
- Users should apply the corrective versions released by Microsoft.
AI-assisted analysis generated from the source advisory — verify against the original.
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Details
Original advisory: https://www.cert.ssi.gouv.fr/alerte/CERTFR-2026-ALE-005/
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Exploitation confirmedCVE-2026-42897Already exploited in the wild (CISA KEV) — the prediction phase is over. Patch now. Riskier than 92% of all scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-42897 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
- critical[UPDATE] [critical] Microsoft Windows products: Multiple vulnerabilitiescert-bund
- unknownexploitedSecurity Alert: Microsoft Releases June 2026 Security Updatesjpcert
- criticalexploitedCVE-2026-42897: Microsoft Exchange Server Cross-Site Scripting Vulnerabilitycisa-kev
Recent advisories for Microsoft Exchange Server
A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.
- highCVE-2026-45503: Microsoft Exchange Server Information Disclosure Vulnerabilitymsrc · 2026-06-09
- highCVE-2026-45504: Microsoft Exchange Server Elevation of Privilege Vulnerabilitymsrc · 2026-06-09
- mediumCVE-2026-45501: Microsoft Exchange Server Spoofing Vulnerabilitymsrc · 2026-06-09
- mediumCVE-2026-45500: Microsoft Exchange Server Spoofing Vulnerabilitymsrc · 2026-06-09
- mediumCVE-2026-45502: Microsoft Exchange Server Information Disclosure Vulnerabilitymsrc · 2026-06-09
- highCVE-2026-45583: Microsoft Exchange Server Remote Code Execution Vulnerabilitymsrc · 2026-06-09
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