Security readout for executives and security teams
Plain-English summary
This critical SharePoint flaw can let an unauthenticated remote attacker run code on a vulnerable server. Successful compromise could expose information, alter content, disrupt service, and provide a foothold into connected systems. CISA’s Known Exploited Vulnerabilities listing confirms active exploitation, making prompt remediation necessary.
Executive priority
Treat this as an immediate remediation priority. The vulnerability permits unauthenticated remote code execution, carries a 9.8 CVSS score, and is listed by CISA as actively exploited. Leadership should require rapid inventory, patch verification, exposure reduction, and compromise review, with exceptions explicitly tracked.
Technical view
CVE-2026-58644 is a CWE-502 deserialization vulnerability affecting specified SharePoint Server products. It is remotely reachable, requires no privileges or user interaction, and has low attack complexity. Its CVSS 3.1 score is 9.8, with high confidentiality, integrity, and availability impact.
Likely exposure
Exposure applies to network-accessible Microsoft SharePoint Enterprise Server 2016, SharePoint Server 2019, and SharePoint Server Subscription Edition deployments identified in the advisory. The supplied version data lists 16.0.0 for each product but does not provide precise vulnerable build ranges, so administrators should confirm applicability through Microsoft’s advisory.
Exploitation context
CISA lists CVE-2026-58644 in its Known Exploited Vulnerabilities catalog, supporting active exploitation in the wild. The source bundle does not describe observed campaigns, attacker identities, exploitation volume, indicators of compromise, or whether public exploit code exists.
Researcher notes
The confirmed weakness is deserialization of untrusted data, classified as CWE-502. The supplied evidence does not identify the vulnerable component, serialized object format, request path, indicators, root-cause details, or exploit prerequisites beyond the CVSS vector. Use Microsoft’s advisory for build-level applicability and remediation specifics.
Mitigation direction
- Review Microsoft’s advisory immediately for applicable security updates and deployment instructions.
- Inventory deployments of the three affected SharePoint Server products.
- Apply Microsoft’s security update according to vendor guidance and organizational change controls.
- Prioritize externally reachable or otherwise broadly network-accessible SharePoint servers.
- Follow current Microsoft guidance for any temporary mitigations if patching cannot occur immediately.
Validation and detection
- Confirm each SharePoint product, edition, version, and installed build against Microsoft’s advisory.
- Verify the applicable Microsoft security update is installed successfully on every affected server.
- Reassess network accessibility and ensure only required systems and users can reach SharePoint.
- Review security telemetry for unexplained code execution, process activity, or configuration changes around SharePoint.
- Confirm backup and recovery procedures are operational before and 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-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-2026-58644 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
- Yes
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/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:N/UI:N/S:U/C:H/I:H/A:H/E:F/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:F/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-2026-58644 added to CISA KEV
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
- 2026-07-16T00:00:00.000Z: CVE-2026-58644 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-2026-58644CVE 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.