Summary
CoreWCF: WS-Security signature substitution via document-wide Signature lookup
Preconditions
Exploitation requires the endpoint be configured with an endorsing supporting token binding, and the attacker constructs a ds:Signature whose KeyInfo resolves through the receive-side token resolver to a key under the attacker’s control. Both are conditions outside the attacker’s direct control on a generic deployment.
Workarounds
Use a security token resolver that only accepts references to issuer-pinned X.509 chains (the default when expecting a static set of signing certificates).
Impact
An unauthenticated remote attacker who can place a SOAP header lexically before wsse:Security can embed a ds:Signature of their choosing inside that header and cause the server to verify the attacker-supplied signature instead of the one carried in the security header.
CVE-2026-54773 has a CVSS score of 5.9 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.8.1, 1.9.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Fixed in CoreWCF v1.8.1 and v1.9.1
Frequently Asked Questions
- What is CVE-2026-54773? CVE-2026-54773 is a medium-severity security vulnerability in CoreWCF.Primitives (nuget), affecting versions < 1.8.1. It is fixed in 1.8.1, 1.9.1.
- How severe is CVE-2026-54773? CVE-2026-54773 has a CVSS score of 5.9 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of CoreWCF.Primitives are affected by CVE-2026-54773? CoreWCF.Primitives (nuget) versions < 1.8.1 is affected.
- Is there a fix for CVE-2026-54773? Yes. CVE-2026-54773 is fixed in 1.8.1, 1.9.1. Upgrade to this version or later.
- Is CVE-2026-54773 exploitable, and should I be worried? Whether CVE-2026-54773 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-54773 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-54773?
- Upgrade
CoreWCF.Primitivesto 1.8.1 or later - Upgrade
CoreWCF.Primitivesto 1.9.1 or later
- Upgrade