CVE Intelligence
Medium Info disclosure

CVE-2021-34485 — .NET Core and Visual Studio Information Disclosure Vulnerability

.NET Core and Visual Studio Information Disclosure Vulnerability

Published Aug 12, 2021 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: microsoft

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 2.1% (30-day exploitation probability)+12
  • Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
2.07%
ahead of 81% of scored CVEs · Oct 15, 2026
Affects
Microsoft
.net and 14 more
CVSS base
5.0
Medium · 5 source(s)
Prioritization reference: 5.5 provisional

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Microsoft .net, Microsoft .NET 5.0, Microsoft .net Core…).
  2. Apply the fixed version or the patch documented under Remediation.
  3. Exploitation requires user interaction: tighten email/web filtering and warn affected users.
  4. Search available logs for exploit probes matching the vulnerability class (info disclosure), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Microsoft .net ≥ 5.0 and ≤ 5.0.8 Vulnerable NIST National Vulnerability Database
Microsoft .NET 5.0 ≥ 5.0.0 and < 5.0.9 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft .net Core ≥ 2.1 and ≤ 2.1.28≥ 3.1 and ≤ 3.1.17 Vulnerable NIST National Vulnerability Database
Microsoft .NET Core 2.1 ≥ 2.1 and < 2.1.30 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft .NET Core 3.1 ≥ 3.1 and < 3.1.18 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft Microsoft Visual Studio 2017 version 15.9 (includes 15.0 - 15.8) ≥ 15.9.0 and < 15.9.38 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft Microsoft Visual Studio 2019 version 16.10 (includes 16.0 - 16.9) ≥ 16.10.0 and < 16.10.5 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft Microsoft Visual Studio 2019 version 16.4 (includes 16.0 - 16.3) ≥ 16.0 and < 16.4.25 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft Microsoft Visual Studio 2019 version 16.7 (includes 16.0 – 16.6) ≥ 16.0.0 and < 16.7.18 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft Microsoft Visual Studio 2019 version 16.9 (includes 16.0 - 16.8) ≥ 15.0.0 and < 16.9.10 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft PowerShell 7.0 ≥ 7.0.0 and < 7.0.7 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft PowerShell 7.1 ≥ 7.1.0 and < 7.1.4 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft Powershell Core ≥ 7.0 and < 7.0.7≥ 7.1 and < 7.1.4 Vulnerable NIST National Vulnerability Database
Microsoft Visual Studio 2017 ≥ 15.0 and ≤ 15.9 Vulnerable NIST National Vulnerability Database
Microsoft Visual Studio 2019 ≥ 16.0 and ≤ 16.10 Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
5.5 CVSS 3.1 Medium 1.8 3.6 nvd@nist.gov via NIST National Vulnerability Database
5.0 CVSS 3.1 Medium 1.3 3.6 secure@microsoft.com via NIST National Vulnerability Database
5.0 CVSS 3.1 Medium 1.3 3.6 134c704f-9b21-4f2e-91b3-4a467353bcc0 via NIST National Vulnerability Database
5.0 CVSS 3.1 Medium — — microsoft via CVE Program (cve.org) e CISA ADP
5.0 CVSS 3.1 Medium — — CISA-ADP via CVE Program (cve.org) e CISA ADP
2.1 CVSS 2.0 Low 3.9 2.9 nvd@nist.gov via NIST National Vulnerability Database
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N (score shown at the top: secure@microsoft.com)
Scoring entities (NIST, CNA, ADP) score independently; each score is shown with its origin. For prioritization we use 5.5 (NVD (NIST)) as a conservative provisional reference — not a definitive official score.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-200 · Exposure of Sensitive Information

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 2.07%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
  • Look for anomalous data read/export volumes and access to sensitive records.
endpoint telemetry (EDR)application logsauthentication logs

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · microsoft/.net 5.0, microsoft/.net core 2.1, microsoft/.net core 3.1, microsoft/microsoft visual studio 2017 version 15.
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Fix documented
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 5.0
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Modified
    Oct 13, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 13, 2026 · NIST National Vulnerability Database
  • 2021
  • CVE published
    Aug 12, 2021 · microsoft

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

2 on the record

Elsewhere on this site

Microsoft
every CVE for this vendor
Info disclosure
same class
CWE-200
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-71328 .NET and Visual Studio Remote Code Execution Vulnerability Sep 8, 2026
  • CVE-2026-69806 .NET Elevation of Privilege Vulnerability Sep 8, 2026
  • CVE-2026-69439 .NET and Visual Studio Elevation of Privilege Vulnerability Sep 8, 2026
  • CVE-2026-69304 ASP.NET Core Denial of Service Vulnerability Sep 8, 2026
  • CVE-2026-58649 .NET Information Disclosure Vulnerability Sep 8, 2026
  • CVE-2026-70354 .NET Core Remote Code Execution Vulnerability Aug 11, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2021-34485 is ".NET Core and Visual Studio Information Disclosure Vulnerability", rated Medium. It affects .net (Microsoft); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.0 describes technical severity. EPSS 2.07% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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