Security readout for executives and security teams
Plain-English summary
This vulnerability can let an unauthenticated remote attacker make an affected ASP.NET Core Kestrel server consume excessive CPU using crafted QUIC traffic. The business impact is service degradation or outage, not data theft. Internet-facing .NET services using HTTP/3 deserve prompt attention.
Executive priority
High priority for externally reachable .NET services because exploitation requires no authentication and can affect availability. Patch during the next urgent maintenance window, prioritizing HTTP/3-enabled public services.
Technical view
CVE-2026-25667 affects ASP.NET Core Kestrel in Microsoft .NET 8.0 before 8.0.22 and .NET 9.0 before 9.0.11. The issue is an incorrect exit condition in HTTP/3 Encoder/Decoder stream processing, reachable through crafted QUIC packets, causing excessive CPU consumption. CVSS is 7.5, AV:N/AC:L/PR:N/UI:N, availability impact high.
Likely exposure
Highest exposure is Kestrel-based ASP.NET Core applications using affected .NET 8 or .NET 9 versions with HTTP/3/QUIC reachable over the network, especially internet-facing services.
Exploitation context
The CVE references public GitHub research and a .NET commit, but the provided sources do not show CISA KEV listing or confirmed active exploitation. Treat the public references as increasing attacker awareness, not proof of in-the-wild exploitation.
Researcher notes
Evidence supports a network DoS in Kestrel HTTP/3 QUIC processing. Affected version detail comes from the CVE description. The source bundle does not provide full product CPEs or operational mitigations beyond fixed versions. Avoid assuming exposure where HTTP/3 or QUIC is not enabled.
Mitigation direction
- Upgrade .NET 8 deployments to 8.0.22 or later.
- Upgrade .NET 9 deployments to 9.0.11 or later.
- Prioritize internet-facing Kestrel services using HTTP/3 or QUIC.
- Review Microsoft and .NET guidance for any environment-specific workarounds.
Validation and detection
- Inventory ASP.NET Core services using Kestrel.
- Confirm deployed runtime versions for .NET 8 and .NET 9.
- Identify whether HTTP/3 or QUIC is enabled and externally reachable.
- Monitor affected services for abnormal CPU spikes and availability degradation.
- Verify patched runtime versions after updates.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-400: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-25667 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Uncontrolled Resource Consumption
Uncontrolled Resource Consumption represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.