CVE-2025-55315: ASP.NET Security Feature Bypass Vulnerability

38

Moderate

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

Exploit-DB · 1

How the score was calculated

Public exploit/PoC (exploitdb)+8
EPSS 65.9% (30-day exploitation probability)+15
Technical severity (critical)+10
CISA SSVC: exploitation "poc"+5

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

65.94%

ahead of 99% of scored CVEs · Oct 14, 2026

Affects

Microsoft

Asp.net Core and 7 more

CVSS base

9.9

Critical · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

Proof of concept

none · proof-of-concept · active

Automatable

No

can an attacker script the kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Microsoft Asp.net Core, Microsoft ASP.NET Core 2.3, Microsoft ASP.NET Core 8.0…).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
EPSS ahead of 99% of scored CVEs: prioritize it in the patch queue.
Search available logs for exploit probes matching the vulnerability class (injection), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Microsoft	Asp.net Core	≥ 2.3.0 and < 2.3.6≥ 8.0.0 and < 8.0.21≥ 9.0.0 and < 9.0.10	Vulnerable	NIST National Vulnerability Database
Microsoft	ASP.NET Core 2.3	≥ 2.3 and < 2.3.6	Vulnerable	CVE Program (cve.org) e CISA ADP
Microsoft	ASP.NET Core 8.0	≥ 8.0 and < 8.0.21	Vulnerable	CVE Program (cve.org) e CISA ADP
Microsoft	ASP.NET Core 9.0	≥ 9.0 and < 9.0.10	Vulnerable	CVE Program (cve.org) e CISA ADP
Microsoft	Microsoft Visual Studio 2022 version 17.10	≥ 17.10.0 and < 17.10.20	Vulnerable	CVE Program (cve.org) e CISA ADP
Microsoft	Microsoft Visual Studio 2022 version 17.12	≥ 17.12.0 and < 17.12.13	Vulnerable	CVE Program (cve.org) e CISA ADP
Microsoft	Microsoft Visual Studio 2022 version 17.14	≥ 17.14.0 and < 17.14.17	Vulnerable	CVE Program (cve.org) e CISA ADP
Microsoft	Visual Studio 2022	≥ 17.10.0 and < 17.10.20≥ 17.12.10 and < 17.12.13≥ 17.14.0 and < 17.14.17	Vulnerable	NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

Low

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
9.9	CVSS 3.1	Critical	3.1	6.0	secure@microsoft.com via NIST National Vulnerability Database
9.9	CVSS 3.1	Critical	—	—	microsoft via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L (score shown at the top: secure@microsoft.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-444 · HTTP Request Smuggling

Other CVEs with this weakness →

Public exploits, PoCs and detection templates

Public code that demonstrates or tests the flaw raises the odds of mass exploitation — and Nuclei templates help find vulnerable assets in your environment.

Exploit-DB

ASP.net 8.0.10 - Bypass Apr 6, 2026

Warning: public PoCs are sometimes disguised malware. Use them only for authorized testing in an isolated environment. This portal does not host exploit code — it only points to the sources.

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 65.94%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Look for parameters with command/query metacharacters and unexpected child processes of the service.

web/proxy/WAF logsnetwork IDS/IPSapplication logsendpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

2026
Affected products added · microsoft/asp.net core 2.3, microsoft/asp.net core 8.0, microsoft/asp.net core 9.0, microsoft/microsoft visual studio 20
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 9.9
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Modified
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
2025
CVE published
Oct 14, 2025 · microsoft

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

3 on the record

msrc.microsoft.com/update-guide/vulnerability/CVE-2025-55315
Vendor Advisory, vendor-advisory, patch, NIST National Vulnerability Database
andrewlock.net/understanding-the-worst-dotnet-vulnerability-request-smuggling-and-cv
NIST National Vulnerability Database
gist.github.com/N3mes1s/d0897c13ca199e739ecc2b562f466040
NIST National Vulnerability Database

Elsewhere on this site

Microsoft
every CVE for this vendor

Injection
same class

CWE-444
other pages naming this weakness

Related CVEs (same products)

High CVE-2026-109468 ASP.NET Core Denial of Service Vulnerability 2h
High CVE-2026-96957 .NET Security Feature Bypass Vulnerability 2d
High CVE-2026-96236 ASP.NET Core Denial of Service Vulnerability 2d
Medium CVE-2026-96234 .NET Information Disclosure Vulnerability 2d
High CVE-2026-96235 .NET Remote Code Execution Vulnerability 2d
High CVE-2026-96237 .NET Remote Code Execution Vulnerability 2d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-55315 is "ASP.NET Security Feature Bypass Vulnerability", rated Critical. It affects Asp.net Core (Microsoft); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.9 describes technical severity. EPSS 65.94% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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