Cyber Resilience

CVE-2025-55315

Microsoft Asp.Net Core 2.3.0 – 2.3.6

High EPSS
Published
14 October 2025
Modified
28 October 2025
Patch / advisory
View advisory
CVSS Score v3.1 9.9
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L
EPSS Score 0.66 99.2th percentile
Risk Priority 92 floored blend · peak EPSS

Summary

CVE-2025-55315 is a critical-severity HTTP Request/Response Smuggling (CWE-444) vulnerability in Microsoft Asp.Net Core. Its CVSS base score is 9.9 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 0.8% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SC-7 (Boundary Protection) and SI-10 (Information Input Validation) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2025-55315 is a critical vulnerability in ASP.NET Core stemming from inconsistent interpretation of HTTP requests, enabling HTTP request/response smuggling as defined by CWE-444. Published on 2025-10-14, it carries a CVSS v3.1 base score of 9.9 (AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L), indicating network-accessible exploitation with low complexity and privileges required.

An authorized attacker with low privileges (PR:L) can exploit this vulnerability over the network without user interaction. Exploitation allows bypassing security features, resulting in high confidentiality and integrity impacts, low availability impact, and a change in scope due to the smuggling mechanism.

Microsoft's Security Response Center provides update guidance at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-55315. Additional technical details are available in Andrew Lock's analysis at https://andrewlock.net/understanding-the-worst-dotnet-vulnerability-request-smuggling-and-cve-2025-55315/ and a GitHub gist at https://gist.github.com/N3mes1s/d0897c13ca199e739ecc2b562f466040.

OWASP Top 10 for Web (2025)

A06:2025 Insecure Design

EU & UK References

Vulnerability Data

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.

CWE(s)
CWE-444

Related Threats

MITRE ATT&CK Enterprise Techniques

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2024-21386Same product: Microsoft Asp.Net Core
CVE-2024-21404Same product: Microsoft Asp.Net Core
CVE-2023-36038Same product: Microsoft Asp.Net Core
CVE-2023-36558Same product: Microsoft Asp.Net Core
CVE-2023-35391Same product: Microsoft Asp.Net Core
CVE-2024-49044Same product: Microsoft Visual Studio 2022
CVE-2021-26855Same vendor: Microsoft
CVE-2024-29053Same vendor: Microsoft
CVE-2022-41040Same vendor: Microsoft
CVE-2023-41763Same vendor: Microsoft

Affected Assets

microsoft
asp.net core
2.3.0 — 2.3.6 · 8.0.0 — 8.0.21 · 9.0.0 — 9.0.10
microsoft
visual studio 2022
17.10.0 — 17.10.20 · 17.12.10 — 17.12.13 · 17.14.0 — 17.14.17

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V4.1.3
  • V4.2.4
  • V1.5.3
  • V4.1.1

Mitigating Controls (NIST 800-53 r5) AI

SC-7 Boundary Protection partial match

Boundary protection at external interfaces can enforce consistent HTTP request/response parsing rules between intermediaries and endpoints.

SI-10 Information Input Validation partial match

Validating HTTP inputs at the intermediary prevents malformed messages from being interpreted inconsistently downstream.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-01 mostly match
prevents

Configuration management can enforce uniform HTTP parsing rules across intermediaries, directly mitigating inconsistent interpretation.

DE.CM-01 partial match
prevents

Network monitoring can detect smuggling attempts via anomalous HTTP traffic or logs, while eliminating the inconsistency directly aids detection of such events.

PR.IR-01 partial match
prevents

Network protections can enforce consistent HTTP proxy/firewall behavior to block smuggling, and removing the weakness helps prevent unauthorized access via request smuggling.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can detect HTTP request smuggling vulnerabilities in intermediary components.

A.8.20 Networks security partial match
degrades

Network security controls can enforce consistent HTTP parsing and proxy behavior that mitigates request smuggling.

A.8.21 Security of network services partial match
degrades

Secure network services include hardening proxies and gateways against inconsistent HTTP interpretation.

A.8.25 Secure development life cycle partial match
prevents

Secure SDLC practices require threat modeling and testing for HTTP parsing inconsistencies in intermediaries.

A.8.26 Application security requirements partial match
prevents

Application security requirements can mandate strict HTTP message validation and canonicalization.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles include consistent protocol handling and defense-in-depth for proxies.

References