CVE-2026-26171: .NET Denial of Service Vulnerability
CVE-2026-26171 is a denial of service vulnerability in .NET, rated Important by Microsoft, with a CVSS 3.1 base score of 7.5 (High). An attacker can exploit it remotely over the network, without any privileges and without user interaction. Microsoft has not reported exploitation in the wild and rates exploitation as less likely. The EPSS model estimates a 1.75% probability of exploitation activity in the next 30 days, higher than 78% of all scored vulnerabilities. Microsoft released the fix on 14 April 2026 in the April 2026 Patch Tuesday, delivered through 3 security updates (KB5086095, KB5086096, KB5086097). It affects 10 products in 1 product family (Developer Tools).
Key facts
- CVE ID
- CVE-2026-26171
- Severity
- High CVSS 7.5
- Microsoft severity
- Important
- Impact
- Denial of Service
- Exploited in the wild
- No
- Publicly disclosed
- No
- Exploitation likelihood
- Less Likely
- Weakness
- CWE-400; CWE-611
- EPSS
- 1.75% (percentile 78%)
- CISA KEV
- Not listed
- Released
- Last updated
- Patch Tuesday
- April 2026 Patch Tuesday
- Product families
- Developer Tools
CVSS score and vector
Microsoft scores CVE-2026-26171 at 7.5 (temporal 6.5) using CVSS 3.1. Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C
| Metric | Value |
|---|---|
| Attack vector | Network |
| Attack complexity | Low |
| Privileges required | None |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality impact | None |
| Integrity impact | None |
| Availability impact | High |
| Exploit code maturity | Unproven |
| Remediation level | Official fix |
| Report confidence | Confirmed |
Description
Uncontrolled resource consumption in .NET allows an unauthorized attacker to deny service over a network.
Affected products (10)
Developer Tools
| Product | Security update | Type | Fixed build | Restart |
|---|---|---|---|---|
| PowerShell 7.5 | Release Notes | Security Update | 7.5.6 | Maybe |
| .NET 10.0 installed on Linux | KB5086095 | Security Update | 10.0.6 | Maybe |
| .NET 8.0 installed on Windows | KB5086096 | Security Update | 8.0.26 | Maybe |
| .NET 10.0 installed on Mac OS | KB5086095 | Security Update | 10.0.6 | Maybe |
| .NET 8.0 installed on Linux | KB5086096 | Security Update | 8.0.26 | Maybe |
| .NET 8.0 installed on Mac OS | KB5086096 | Security Update | 8.0.26 | Maybe |
| .NET 9.0 installed on Linux | KB5086097 | Security Update | 9.0.15 | Maybe |
| .NET 9.0 installed on Windows | KB5086097 | Security Update | 9.0.15 | Maybe |
| .NET 9.0 installed on Mac OS | KB5086097 | Security Update | 9.0.15 | Maybe |
| PowerShell 7.6 |
Security updates (3)
NIST NVD data
Affected configurations (CPE)
| Product | Vulnerable versions |
|---|---|
| .net | from 10.0.0, before 10.0.6 |
| .net | from 8.0.0, before 8.0.26 |
| .net | from 9.0.0, before 9.0.15 |
| powershell | from 7.5, before 7.5.6 |
| powershell | from 7.6, before 7.6.1 |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26171 (Vendor Advisory)
Acknowledgments
- Ludvig Pedersen
Revision history
| Version | Date | Description |
|---|---|---|
| 1.0 | Information published. | |
| 2.0 | The CVE was updated to links to security updates for Powershell 7.6 and 7.5. Microsoft recommends installing these updates as soon as possible. |