Service interruption via retained malicious client connections
Published Aug 8, 2023 · Updated Aug 10, 2026
Denial of service in Microsoft Kestrel in ASP.NET Core 2.1, .NET 6.0, and .NET 7.0 allows remote attackers to exhaust server resources. After detecting a potentially malicious HTTP client, Kestrel sometimes retains the connection instead of disconnecting it, allowing connections to consume resources. Directly reachable Kestrel endpoints are exposed; a reverse proxy or web application firewall with HTTP-attack protections can block the triggering traffic.
Summary
What happened
Denial of service in Microsoft Kestrel in ASP.NET Core 2.1, .NET 6.0, and .NET 7.0 allows remote attackers to exhaust server resources. After detecting a potentially malicious HTTP client, Kestrel sometimes retains the connection instead of disconnecting it, allowing connections to consume resources. Directly reachable Kestrel endpoints are exposed; a reverse proxy or web application firewall with HTTP-attack protections can block the triggering traffic.
The record
- CVE
- CVE-2023-38180
- Published
- Aug 8, 2023
- Updated
- Aug 10, 2026
- Vendor
- Microsoft
- Product
- .NET 6.0
- Classifications
- CWE-400, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 8, 2023CVE publishedPublication date reported by the CVE source.
- Aug 9, 2023Exploitation reportedCISA Known Exploited Vulnerabilities catalog listing
- Aug 10, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=6.0.0 <6.0.21
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Reported exploitation
- CISA Known Exploited Vulnerabilities catalog listingknown exploited catalog
Technologies
Your stack
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Your stack
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