Security readout for executives and security teams
Plain-English summary
A user who already has limited authorized access to an affected on-premises Microsoft Exchange server may gain higher local privileges. Successful exploitation could expose email data, permit unauthorized changes, or disrupt the server. The supplied sources rate the issue high severity, but do not establish active exploitation.
Executive priority
Treat this as a high-priority patching task, especially where Exchange supports critical communications or local access is broadly granted. It is not evidence of an unauthenticated remote compromise, but successful privilege escalation could produce complete confidentiality, integrity, and availability impact on the server.
Technical view
CVE-2026-55006 is a local privilege-escalation flaw caused by insufficiently granular access control in Microsoft Exchange Server. CVSS 3.1 is 7.8: local access, low complexity, low privileges, no user interaction, unchanged scope, and high confidentiality, integrity, and availability impact.
Likely exposure
Exposure is limited to the listed Exchange 2016 CU23, Exchange 2019 CU14 and CU15, and Subscription Edition RTM deployments. The attacker must already have authorized, low-privileged local access. The bundle does not identify cloud-hosted Exchange Online as affected.
Exploitation context
The supplied record is not marked as CISA KEV and provides no evidence of active exploitation or a public exploit. Exploitation requires local, authorized access, reducing initial reach but making compromised accounts, insiders, and existing server footholds relevant risk contexts.
Researcher notes
The record maps the weakness to CWE-1220 and describes insufficient access-control granularity. The bundle does not disclose the vulnerable component, attack mechanics, indicators, fixed build numbers, or public proof of concept. Researchers should use Microsoft’s advisory for authoritative update applicability without assuming unlisted versions are affected.
Mitigation direction
- Review the Microsoft advisory and apply its security update to every affected Exchange server.
- Prioritize internet-facing or business-critical Exchange servers, while recognizing exploitation itself requires local access.
- Restrict local and administrative access to Exchange hosts until remediation is confirmed.
- Monitor Microsoft guidance for revised affected-version or remediation information.
Validation and detection
- Inventory Exchange editions, cumulative updates, and exact build versions across all environments.
- Compare each server against the affected products and versions in the Microsoft advisory.
- Verify the applicable Microsoft security update installed successfully on each affected server.
- Review privileged-group membership and recent privilege changes for unexpected activity.
- Confirm Exchange services and mail flow remain healthy after remediation.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-1220: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupPrivilege behavior lookup
The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-55006 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C1.85.9microsoftVulnerability scoring details
Base CVSS 3.1 score
7.8HighVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- Microsoft Exchange Server Elevation of Privilege VulnerabilityCVE reference, microsoft · vendor-advisory, patch
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Insufficient Granularity of Access Control
Insufficient Granularity of Access Control represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.