CVE-2026-55006
Microsoft Exchange Server 2016 … 2019
Raw vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HSummary
CVE-2026-55006 is a high-severity Insufficient Granularity of Access Control (CWE-1220) vulnerability in Microsoft Exchange Server. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 12th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-3 (Access Enforcement) and AC-6 (Least Privilege) — see the control section below for these in your framework.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-44025
Vulnerability Data
Insufficient granularity of access control in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Direct local privilege escalation via insufficient access control granularity in Exchange Server.
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
Mitigating Controls (NIST 800-53 r5) AI
Directly enforces fine-grained authorization decisions that the CVE shows are insufficient, blocking unauthorized privilege elevation.
Requires assignment of only the minimum privileges needed, directly countering the overly broad access that enables local escalation in Exchange.
Enforces information flow rules between subjects and objects, providing additional granularity that can limit the scope of an authorized user's actions.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
PR.IR-01's segmentation + zero-trust rules directly enforce minimum-necessary access at network boundaries, removing most instances of overly broad policy; CWE-1220 can still exist in application-layer or intra-segment controls that this single outcome does not address.
PR.PS-06's general SDLC practices can surface granularity issues during design/review (partial prevention) but do not specifically target access-control policy breadth, so they remove only part of CWE-1220's risk.
CWE-1220 permits unauthorized access to sensitive assets but neither prevents nor impairs the delivery of adverse-event information to authorized recipients.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Directly requires information-access restriction at the level of individual assets and operations, addressing the granularity gap.
Establishes the overarching access-control policy whose granularity directly determines whether the weakness exists.
Defines the assignment and review of access rights; insufficient granularity in those rights is the root of CWE-1220.
Specifies management of privileged access rights, where overly broad privileges are a common manifestation of the weakness.
Limits use of privileged utilities; overly coarse access rules can still allow unauthorized utility access.