CVE-2021-26418: Microsoft SharePoint Server Spoofing Vulnerability
Noroxi assessment
Priority: Monitor (action score 18/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 1.2% (FIRST EPSS); higher than 69.2% of all records.
- Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. A user must open a link or visit a page. No special conditions are required; it is repeatable.
- According to the record, no fixed version is available yet.
Low priority for now. Update when a fix is released; follow the vendor's advisory.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
- Published
- May 11, 2021
- Updated
- Jun 16, 2026
- EPSS
- 1.2% · 69th percentile
- CWE
- CWE-290
Report tools
Action score
18
Monitor
Low priority for now.
- CVSS
- 18 / 40 · 4.6 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 1.2%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · microsoft
- 4.6
- NVD has not scored this yet; the score shown is the CNA’s.
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N/E:U/RL:O/RC:C
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- No fixed version yet
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| microsoft | sharepoint foundation | cpe:2.3:a:microsoft:sharepoint_foundation |
| microsoft | sharepoint server | cpe:2.3:a:microsoft:sharepoint_server |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- microsoft sharepoint foundation2013
- microsoft sharepoint server2016
- microsoft sharepoint server2019
Versions reported by the vendor
Affected version ranges reported by the assigning authority (microsoft). Independent of NVD's CPE analysis and usually ahead of it.
Microsoft Microsoft SharePoint Enterprise Server 2016
- 16.0.0 and later · before 16.0.5161.1000affected
Microsoft Microsoft SharePoint Foundation 2013 Service Pack 1
- 15.0.0 and later · before 15.0.5345.1000affected
Microsoft Microsoft SharePoint Server 2019
- 16.0.0 and later · before 16.0.10374.20000affected
Same product
microsoft: all recordsOther highest-scoring records for the same primary product.
- CVE-2022-44690Microsoft SharePoint Server Remote Code Execution Vulnerability60This week
- CVE-2023-21742Microsoft SharePoint Server Remote Code Execution Vulnerability52Plan
- CVE-2021-28474Microsoft SharePoint Server Remote Code Execution Vulnerability50Plan
Published before and after this one in the same product
- ← EarlierCVE-2021-1718Jan 12, 2021 · Microsoft SharePoint Server Tampering Vulnerability33Monitor
- ← EarlierCVE-2021-28450Apr 13, 2021 · Microsoft SharePoint Denial of Service Vulnerability21Monitor
- Later →CVE-2021-28478May 11, 2021 · Microsoft SharePoint Server Spoofing Vulnerability30Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
No fix version is recorded for this entry. Check the references for vendor advisories.
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
No history yet (it accumulates with the daily EPSS job).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
—
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
- CVE-2021-284740 days apartMicrosoft SharePoint Server Remote Code Execution Vulnerability50Plan
- CVE-2021-3195028 days apartMicrosoft SharePoint Server Spoofing Vulnerability31Monitor
- CVE-2021-3196328 days apartMicrosoft SharePoint Server Remote Code Execution Vulnerability29Monitor
- CVE-2021-3196628 days apartMicrosoft SharePoint Server Remote Code Execution Vulnerability29Monitor
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- A low-privileged account is enough.
- A user must open a link or visit a page.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- low · data can be read
- Integrity
- low · data or configuration can be modified
- Availability
- none
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality impact
- Low
- Integrity impact
- Low
- Availability impact
- None
Weakness class (CWE)
CWE-290 · Authentication Bypass by SpoofingCVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- Exploitation of Trusted IdentifiersCAPEC-21likelihood: High · High
- Exploiting Trust in ClientCAPEC-22likelihood: High · High
- Creating a Rogue Certification Authority CertificateCAPEC-459likelihood: Medium · Very High
- Web Services API Signature Forgery Leveraging Hash Function Extension WeaknessCAPEC-461High
- Signature SpoofCAPEC-473
- Signature Spoofing by MisrepresentationCAPEC-476likelihood: Low · High
- Session Credential Falsification through PredictionCAPEC-59likelihood: High · High
- Reusing Session IDs (aka Session Replay)CAPEC-60likelihood: High · High
ATT&CK techniques
- Masquerading: Invalid Code SignatureT1036.001
- Access Token ManipulationT1134
- Access Token Manipulation:Token Impersonation/TheftT1134.001
- Steal Application Access TokenT1528
- Steal Web Session CookieT1539
- Use Alternate Authentication Material:Web Session CookieT1550.004
- Subvert Trust Controls: Code SigningT1553.002
- Adversary-in-the-MiddleT1557
Change log
No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.
References
Vendor advisories and official records. Exploit/PoC links are deliberately left out.