Summary
CoreWCF: XML Signature Wrapping in WS-Security endorsing/supporting signature verification allows replay of captured signed messages
Workarounds
Ensure communication is protected by SSL/TLS to prevent capturing of signed SOAP envelope.
Impact
The attacker, with one captured signed SOAP envelope from a victim and no other privileges, can invoke arbitrary operations on the service as the victim principal for the lifetime of the captured signing key. There is no rate limit on replays. The DetectReplays setting on transport-security bindings does not mitigate the issue because the attack does not reuse the original timestamp, the fresh timestamp in the wsse:Security header is what the replay-detection logic inspects.
CVE-2026-54783 has a CVSS score of 7.4 (High). 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-2026-54783? CVE-2026-54783 is a high-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-2026-54783? CVE-2026-54783 has a CVSS score of 7.4 (High). 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-2026-54783? CoreWCF.Primitives (nuget) versions < 1.8.1 is affected.
- Is there a fix for CVE-2026-54783? Yes. CVE-2026-54783 is fixed in 1.8.1, 1.9.1. Upgrade to this version or later.
- Is CVE-2026-54783 exploitable, and should I be worried? Whether CVE-2026-54783 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-2026-54783 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-2026-54783?
- Upgrade
CoreWCF.Primitivesto 1.8.1 or later - Upgrade
CoreWCF.Primitivesto 1.9.1 or later
- Upgrade