ASP.NET Core 2.3: Inconsistent Interpretation of HTTP Requests
CVE-2025-55315 is a critical-severity inconsistent interpretation of HTTP requests vulnerability in ASP.NET Core 2.3 from Microsoft, with a CVSS 3.1 base score of 9.9 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists version 2.3.6 as the first without the flaw, so updating ASP.NET Core 2.3 to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 67.2% chance of exploitation within 30 days, which is in the top 0.69% of all scored CVEs.
Exploitation in the next 30 days is more likely than not, according to EPSS.
What to do
- Update ASP.NET Core 2.3 to 2.3.6 or a later version.
- Update ASP.NET Core 8.0 to 8.0.21 or a later version.
- Update ASP.NET Core 9.0 to 9.0.10 or a later version.
- Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Microsoft | ASP.NET Core 2.3 | 2.3 up to, but not including, 2.3.6 | 2.3.6 |
| Microsoft | ASP.NET Core 8.0 | 8.0 up to, but not including, 8.0.21 | 8.0.21 |
| Microsoft | ASP.NET Core 9.0 | 9.0 up to, but not including, 9.0.10 | 9.0.10 |
| Microsoft | Microsoft Visual Studio 2022 version 17.10 | 17.10.0 up to, but not including, 17.10.20 | 17.10.20 |
| Microsoft | Microsoft Visual Studio 2022 version 17.12 | 17.12.0 up to, but not including, 17.12.13 | 17.12.13 |
| Microsoft | Microsoft Visual Studio 2022 version 17.14 | 17.14.0 up to, but not including, 17.14.17 | 17.14.17 |
| Microsoft | Asp.net Core | 2.3.0 up to, but not including, 2.3.6; 8.0.0 up to, but not including, 8.0.21; 9.0.0 up to, but not including, 9.0.10 | 2.3.6, 8.0.21, 9.0.10 |
| Microsoft | Visual Studio 2022 | 17.10.0 up to, but not including, 17.10.20; 17.12.10 up to, but not including, 17.12.13; 17.14.0 up to, but not including, 17.14.17 | 17.10.20, 17.12.13, 17.14.17 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- LowPerformance or availability is reduced.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L. Scored by CNA (microsoft.com).
Official description
Inconsistent interpretation of http requests ('http request/response smuggling') in ASP.NET Core allows an authorized attacker to bypass a security feature over a network.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Inconsistent Interpretation of HTTP Requests
The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.
How developers prevent this class of flaw
- Use a web server that employs a strict HTTP parsing procedure, such as Apache.
- Terminate the client session after each request.
More Inconsistent Interpretation of HTTP Requests vulnerabilities (CWE-444)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
Recent Inconsistent Interpretation of HTTP Requests vulnerabilities
- 7.5 High severity
- 7.5 High severity
- 9.1 Critical severity
- 7.5 High severity
- 8.8 High severity
- 7.5 High severity
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