Security readout for executives and security teams
Plain-English summary
CVE-2026-45659 is a high-severity Microsoft SharePoint flaw that lets a logged-in attacker run code remotely. Because SharePoint often hosts sensitive business documents and workflows, successful exploitation could affect confidentiality, integrity, and availability. CISA KEV status indicates known exploitation, so this should be treated as urgent for exposed SharePoint environments.
Executive priority
Treat as urgent. The combination of remote code execution, high business impact, and CISA KEV listing makes this a priority patching and exposure-reduction item for any affected SharePoint deployment.
Technical view
The vulnerability is deserialization of untrusted data, tracked as CWE-502, in Microsoft Office SharePoint. It affects SharePoint Enterprise Server 2016, SharePoint Server 2019, and SharePoint Server Subscription Edition. CVSS is 8.8 with network attack vector, low complexity, low privileges required, no user interaction, and high CIA impact.
Likely exposure
Organizations running affected on-premises SharePoint versions are the primary concern. Internet-accessible SharePoint sites, partner-facing portals, and environments with many authenticated users have higher practical exposure. The source bundle does not identify SharePoint Online as affected.
Exploitation context
CISA KEV status supports that exploitation is known in the wild. The CVSS vector indicates an authorized attacker can exploit over the network without user interaction. No exploit details, indicators, or specific attack campaigns are provided in the supplied sources.
Researcher notes
Evidence supports affected products, CWE-502 deserialization, CVSS 8.8, official remediation availability, and KEV status. The supplied sources do not provide exploit mechanics, IOCs, vulnerable build ranges beyond listed versions, or compensating controls beyond consulting Microsoft guidance.
Mitigation direction
- Apply the Microsoft security update or guidance from the MSRC advisory.
- Prioritize internet-facing and business-critical SharePoint servers.
- Restrict network access to SharePoint where operationally feasible.
- Review privileged and broad SharePoint user access.
- Monitor vendor and CISA guidance for updates.
Validation and detection
- Inventory SharePoint Enterprise Server 2016, Server 2019, and Subscription Edition instances.
- Confirm installed builds against Microsoft’s advisory.
- Identify internet-exposed SharePoint endpoints.
- Check whether emergency or cumulative updates are installed.
- Review authentication logs for unusual access patterns.
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-502: Code execution behavior lookup
Code execution and unsafe deserialization weaknesses often justify reviewing execution behavior and process telemetry. 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-2026-45659 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
- 8.8 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:N/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.
CISA KEV status
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:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C2.85.9microsoftVulnerability scoring details
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:N/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.
- Added to KEVCISA-ADP
CISA Known Exploited Vulnerabilities metadata lists this CVE as known exploited.
- ADP timelineCISA-ADP
CVE-2026-45659 added to CISA KEV
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
- 2026-07-01T00:00:00.000Z: CVE-2026-45659 added to CISA KEV
Source materials
- CVE List V5 sourceCVE List V5
- Microsoft SharePoint Remote Code Execution VulnerabilityCVE reference, microsoft · vendor-advisory, patch
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-45659CVE reference, CISA-ADP · government-resource
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.
Deserialization of Untrusted Data
Deserialization of Untrusted Data represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.