How severe is CVE-2026-54774?

CVE-2026-54774 has a CVSS score of 7.4/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-54774?

CVE-2026-54774 affects the following packages: CoreWCF.Primitives (NuGet), CoreWCF.Primitives (NuGet). Ecosystems affected: NuGet.

How do I fix CVE-2026-54774?

Update CoreWCF.Primitives to 1.8.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54774 is resolved across your whole dependency graph.

How do I detect CVE-2026-54774 in my NuGet dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for CoreWCF.Primitives, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-54774 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-54774 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-54774 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-54774?

CVE-2026-54774 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 9th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-54774?

CVE-2026-54774 is classified as CWE-345 (CWE-345), CWE-347 (CWE-347). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-54774 published, and has it been updated?

CVE-2026-54774 was published on July 8, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

.NET

.NET NuGet

Not in CISA KEV

HIGH severity

CVE-2026-54774 — CoreWCF.Primitives

HIGHFix: CoreWCF/CoreWCF@65d0902

CVE-2026-54774 is a high-severity (CVSS 7.4) CWE-345 vulnerability in CoreWCF.Primitives. A fix is available for CoreWCF.Primitives — see the affected versions and patch details below.

CoreWCF: SamlSerializer skips SignatureValue verification when SAML signing token is not an X.509 certificate

Also known asGHSA-rpj7-hr7h-w6p9

Published

Jul 8, 2026

Updated

Aug 12, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-54774.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs9th percentile — riskier than 9% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-54774 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 384,189 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

2 pkgs affected

.NETCoreWCF.Primitives.NETCoreWCF.Primitives

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

Description

Impact

When a service is configured to validate SAML tokens using a method other than X.509 certificate signing, the final signature verification is skipped.

Preconditions

The service is configured to authenticate using SAML tokens and an out of band token resolver (commonly the IssuerTokenResolver of IssuedTokenServiceCredential) holds a non-X.509 SecurityToken whose key identifier the attacker can reference in the assertion’s <KeyInfo> - for example a BinarySecretSecurityToken representing the symmetric proof key issued by a WS-Trust symmetric-key holder-of-key STS.

Patches

Fixed in CoreWCF v1.8.1 and v1.9.1

Workarounds

None

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
.NETNuGet	`CoreWCF.Primitives`	all versions	1.8.1`dotnet add package CoreWCF.Primitives --version 1.8.1`
.NETNuGet	`CoreWCF.Primitives`	≥ 1.9.0&&< 1.9.1	1.9.1`dotnet add package CoreWCF.Primitives --version 1.9.1`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for CoreWCF.Primitives, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update CoreWCF.Primitives to 1.8.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54774 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### Impact When a service is configured to validate SAML tokens using a method other than X.509 certificate signing, the final signature verification is skipped. #### Preconditions The service is configured to authenticate using SAML tokens and an out of band token resolver (commonly the IssuerTokenResolver of IssuedTokenServiceCredential) holds a non-X.509 SecurityToken whose key identifier the attacker can reference in the assertion’s `<KeyInfo>` - for example a `BinarySecretSecurityToken` representing the symmetric proof key issued by a WS-Trust symmetric-key holder-of-key STS. ### Patche