How severe is CVE-2021-26423?

CVE-2021-26423 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-26423 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (89th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-26423?

CVE-2021-26423 primarily affects Microsoft .net. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-26423?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-26423 published?

CVE-2021-26423 was published on 2021-08-12 and last updated on 2026-06-17.

CVE-2021-26423

CVE-2021-26423 is a high-severity vulnerability in Microsoft .net with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 4% (89th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Microsoft .net
Published: 2021-08-12
Last modified: 2026-06-17

Description

.NET Core and Visual Studio Denial of Service Vulnerability

Frequently asked questions

What is CVE-2021-26423?: .NET Core and Visual Studio Denial of Service Vulnerability
How severe is CVE-2021-26423?: CVE-2021-26423 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-26423 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (89th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-26423?: CVE-2021-26423 primarily affects Microsoft .net. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-26423?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-26423 published?: CVE-2021-26423 was published on 2021-08-12 and last updated on 2026-06-17.

References

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26423

Affected products (6)

cpe:2.3:a:microsoft:.net:*:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:.net_core:*:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:powershell_core:*:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:visual_studio_2017:*:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:visual_studio_2019:*:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:visual_studio_2019:8.10:*:*:*:*:macos:*:*

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