Security readout for executives and security teams
Plain-English summary
CVE-2021-28478 is a high-severity Microsoft SharePoint Server spoofing issue. An attacker with low privileges could exploit it only with user interaction, but the rated impact includes high confidentiality risk. Organizations using affected on-premises SharePoint versions should verify patch status promptly.
Executive priority
High priority for organizations running affected on-premises SharePoint. It is not marked as known exploited in the provided sources, but SharePoint often stores sensitive business data and should be patched through normal high-severity processes.
Technical view
The issue is classified as CWE-290 and affects SharePoint Enterprise Server 2016, SharePoint Server 2019, and SharePoint Foundation 2013 SP1. CVSS 3.1 is 7.6: network exploitable, low complexity, low privileges required, user interaction required, changed scope, high confidentiality impact, low integrity impact, and no availability impact.
Likely exposure
Exposure is limited to the listed on-premises Microsoft SharePoint products and versions in the source bundle. SharePoint Online or other Microsoft products are not identified as affected in the provided sources.
Exploitation context
The source bundle does not indicate CISA KEV listing or active exploitation. The CVSS vector shows exploitation requires low privileges and user interaction, with exploit code maturity marked unproven.
Researcher notes
The public bundle provides limited vulnerability detail beyond spoofing, CWE-290, affected products, CVSS, and Microsoft advisory reference. Avoid assuming exploit mechanics, affected configurations, or compensating controls not documented in vendor guidance.
Mitigation direction
- Apply Microsoft’s official fix for affected SharePoint products per MSRC guidance.
- Prioritize internet-facing or externally accessible SharePoint farms.
- Check Microsoft guidance for version-specific update prerequisites and supersedence.
- Reduce access to affected SharePoint systems until patch status is confirmed.
Validation and detection
- Inventory SharePoint farms for the affected products and versions listed.
- Confirm installed SharePoint security updates against the MSRC advisory.
- Identify exposed SharePoint sites with external, partner, or broad internal access.
- Document any unpatched systems with business owner and remediation date.
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-290: 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 lookupCVE-2021-28478 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
- 7.6 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N/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.
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:R/S:C/C:H/I:L/A:N/E:U/RL:O/RC:C2.34.7Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.6HighVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N/E:U/RL:O/RC:C
Source materials
- CVE List V5 sourceCVE List V5
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-28478CVE reference · x_refsource_MISC
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.
Authentication Bypass by Spoofing
Authentication Bypass by Spoofing represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.