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CVE-2026-54781— CoreWCF: SAML SubjectConfirmation methods and holder-of-key proof keys are not enforced

Quick assessment

Affected
CoreWCF CoreWCF
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

CoreWCF是CoreWCF团队开源的一个开源项目,旨在为 .NET Core 和 .NET 5+ 提供 WCF(Windows Communication Foundation)的替代实现。 CoreWCF 1.8.1之前版本和1.9.1之前版本存在安全漏洞，该漏洞源于SAML令牌验证未强制实施SubjectConfirmation方法URI或持有者密钥证明，允许持有者密钥降级或自定义确认方法断言，无需证明对断言的授权即可验证主题。

CVSS 7.4 · High EPSS 0.25% · P15

Possible ATT&CK Techniques 1 AI

T1550.004 · Web Session Cookie

Affected Version Matrix 2

VendorProduct Version RangeStatus
CoreWCF CoreWCF >= 1.9.0, < 1.9.1 affected
< 1.8.1 affected
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I. Basic Information for CVE-2026-54781

Vulnerability Information
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Vulnerability Title
CoreWCF: SAML SubjectConfirmation methods and holder-of-key proof keys are not enforced
Source: CVE Program / CVE List V5
Vulnerability Description
CoreWCF is a port of the service side of Windows Communication Foundation (WCF) to .NET Core. Prior to 1.8.1 and 1.9.1, CoreWCF SAML token validation does not enforce SubjectConfirmation method URIs or holder-of-key proof keys in SamlSecurityTokenHandler, allowing holder-of-key downgrade or custom confirmation method assertions to authenticate a subject without proving authority over the assertion. This issue is fixed in versions 1.8.1 and 1.9.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
认证机制不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
CoreWCF 授权问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
CoreWCF是CoreWCF团队开源的一个开源项目,旨在为 .NET Core 和 .NET 5+ 提供 WCF(Windows Communication Foundation)的替代实现。 CoreWCF 1.8.1之前版本和1.9.1之前版本存在安全漏洞，该漏洞源于SAML令牌验证未强制实施SubjectConfirmation方法URI或持有者密钥证明，允许持有者密钥降级或自定义确认方法断言，无需证明对断言的授权即可验证主题。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
CoreWCF CoreWCF >= 1.9.0, < 1.9.1 -

II. Public POCs for CVE-2026-54781

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 11330 chars
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Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
In-depth vulnerability mechanism
Trigger conditions & impact
Full executable POC code
Exploit chain & mitigation
POC zip download
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III. Intelligence Information for CVE-2026-54781

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Patches & Fixes for CVE-2026-54781 (3)

Vendor Advisories for CVE-2026-54781 (1)

Vendor Pages for CVE-2026-54781 (1)

Other References for CVE-2026-54781 (1)

Same Patch Batch · CoreWCF · 2026-07-08 · 13 CVEs total

CVE-2026-54782 10.0 CRITICAL CoreWCF: Authentication bypass in CoreWCF SAML 1.1 / 2.0 token signature validation
CVE-2026-54772 7.5 HIGH CoreWCF: Pre-authentication infinite-loop CPU exhaustion in CoreWCF net.tcp / net.pipe / n
CVE-2026-54783 7.4 HIGH CoreWCF: XML Signature Wrapping in WS-Security endorsing/supporting signature verification
CVE-2026-54774 7.4 HIGH CoreWCF: SamlSerializer skips SignatureValue verification when SAML signing token is not a
CVE-2026-54784 7.4 HIGH CoreWCF: SPNEGO SecurityContextToken proof key wrapped without confidentiality
CVE-2026-54775 6.5 MEDIUM CoreWCF: Kafka consume pump halts permanently on a Kafka tombstone (null-value record), ca
CVE-2026-54777 6.5 MEDIUM CoreWCF NetNamedPipe transport accepts attach to a pre-existing named pipe instance
CVE-2026-54778 6.2 MEDIUM CoreWCF: UnixDomainSocket Non-Reentrant POSIX Identity Resolution
CVE-2026-54779 5.9 MEDIUM CoreWCF: SAML token replay protection is inoperative
CVE-2026-54773 5.9 MEDIUM CoreWCF: WS-Security signature substitution via document-wide Signature lookup
CVE-2026-54776 4.4 MEDIUM CoreWCF: Unix Domain Socket PosixIdentity transport accepts connections that skip the secu
CVE-2026-54780 3.7 LOW CoreWCF: WS-Security Reference DigestMethod Algorithm-Suite Bypass

IV. Related Vulnerabilities

Same product: CoreWCF
Same vendor: CoreWCF
Same weakness: CWE-287

V. Comments for CVE-2026-54781

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