Microsoft Exchange Server: Authorization bypass leading to privilege escalation
Summary
A authorization bypass caused by a user-controlled key in Microsoft Exchange Server Subscription Edition (SE) RTM allows an authenticated attacker to elevate privileges over the network. The attacker needs a valid low-privileged account and no user interaction is required. Successful exploitation could impact the confidentiality, integrity and availability of the mail server and its mailboxes. Technical details are not publicly available and no exploitation has been reported.
Affected
- Microsoft Exchange Server Subscription Edition (SE) RTM, builds 15.02.0.0 before 15.02.2562.057
- Exchange 2016 and 2019 are not listed for this CVE
- Unknown whether other Exchange versions are affected
Fixed in
- Fixed in build 15.02.2562.057 according to the CNA version range
- The KB article delivering this build could not be verified; check the Microsoft Security Update Guide
Workaround
- Unknown. No mitigation found; apply the Microsoft update as the fix.
Exploitation
- Exploited in the wild: no evidence found
- CISA KEV: not listed according to a third-party aggregator; verify on the CISA catalog
- Public proof of concept: none found
- CISA SSVC: exploitation none, automatable no, technical impact total
Our recommendation
- Inventory on-premises Exchange servers and check SE RTM builds against 15.02.2562.057
- Apply the Microsoft update once the MSRC page confirms the KB number
- Confirm that no Exchange 2016 or 2019 servers remain in use
- Limit or monitor internet exposure of OWA and ECP and enforce MFA for mailbox access
- Re-check NVD, CISA KEV and MSRC over the next few days, as the analysis is pending
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Microsoft Exchange Server
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Server software (Exchange, SharePoint …)
- Updates (KB)
- KB5133453
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-118150 msrc.microsoft.com
- CVE Record: CVE-2026-118150 www.cve.org
- Strix AI: CVE-2026-118150 www.strix.ai
- Microsoft Exchange Server SE update KB5129955 (download) www.microsoft.com
- Senserva: KB5129955 senserva.com
- Microsoft Support: Exchange update 2026/5129955 support.microsoft.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 10 Nov 2026, 22:27.
Original description (NVD)
Authorization bypass through user-controlled key in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a network.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
Affected? We can help.
We check whether your systems are affected, install updates and close the gap – continuously with the System Health Checker if you wish.