Security readout for executives and security teams
Plain-English summary
A memory-handling flaw in Microsoft Windows DHCP Server could let an unauthenticated network attacker run code on an affected system. Successful exploitation could compromise confidentiality, integrity, and availability. Because DHCP supports core network operations, disruption or server takeover could have broad business impact.
Executive priority
Treat as an immediate patching priority for operational DHCP servers, especially those reachable across broad or untrusted network segments. Validate exposure promptly, deploy Microsoft’s applicable update under expedited change control, and monitor service stability. Current evidence does not support claiming active exploitation.
Technical view
CVE-2026-56159 is a heap-based buffer overflow (CWE-122) in Windows DHCP Server Service. Its CVSS 3.1 score is 9.8: network-accessible, low complexity, requiring neither privileges nor user interaction. The supplied vector reports unproven exploit maturity, an official fix, and confirmed reporting.
Likely exposure
Exposure is most likely where the DHCP Server Service runs on a listed Windows Server 2012 through 2025 release and is network-reachable. The bundle also lists Windows 10 versions 1607 and 1809. Confirm service deployment, exact operating-system versions, and update status rather than assuming every listed Windows host is vulnerable.
Exploitation context
The bundle does not establish active exploitation, and the CVE is not identified as CISA KEV. The CVSS vector marks exploit maturity as unproven. Nevertheless, unauthenticated network reachability, low attack complexity, and potential code execution make exposed DHCP servers urgent remediation targets.
Researcher notes
The supplied evidence identifies CWE-122 but provides no crash details, vulnerable function, protocol message, proof of concept, or observed exploitation. Avoid inferring exploitability beyond Microsoft’s network RCE classification and CVSS metrics. Product applicability should be validated against the current Microsoft advisory.
Mitigation direction
- Review Microsoft’s CVE advisory and install the applicable security update for each affected system.
- Prioritize network-reachable DHCP servers and other systems confirmed to run the DHCP Server Service.
- Restrict DHCP service reachability to required network segments while updates are being deployed.
- Follow Microsoft guidance for unsupported or legacy Windows Server releases.
Validation and detection
- Inventory systems running the Windows DHCP Server Service.
- Match operating-system editions, versions, and installation types against Microsoft’s affected-product list.
- Verify the applicable Microsoft security update is installed successfully.
- Confirm DHCP functionality after updating and investigate unexpected service failures or crashes.
- Reassess network paths to ensure only required clients and segments can reach the service.
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-122: 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 lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-56159 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
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/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:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C3.95.9microsoftVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/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
- DHCP Server Service Remote Code Execution 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.
Heap-based Buffer Overflow
Heap-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.