How severe is CVE-2026-54773?

CVE-2026-54773 has a CVSS score of 5.9/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-54773?

CVE-2026-54773 affects the following packages: CoreWCF.Primitives (NuGet), CoreWCF.Primitives (NuGet). Ecosystems affected: NuGet.

How do I fix CVE-2026-54773?

Update CoreWCF.Primitives to 1.8.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54773 is resolved across your whole dependency graph.

How do I detect CVE-2026-54773 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-2026-54773 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-2026-54773 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-54773 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-2026-54773?

CVE-2026-54773 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 31th 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-2026-54773?

CVE-2026-54773 is classified as CWE-347 (CWE-347). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-54773 published, and has it been updated?

CVE-2026-54773 was published on July 8, 2026 and was last updated on October 28, 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

MEDIUM severity

CVE-2026-54773 — CoreWCF.Primitives

MEDIUMFix: CoreWCF/CoreWCF@0589692

CVE-2026-54773 is a medium-severity (CVSS 5.9) CWE-347 vulnerability in CoreWCF.Primitives. A fix is available for CoreWCF.Primitives — see the affected versions and patch details below.

CoreWCF: WS-Security signature substitution via document-wide Signature lookup

Also known asGHSA-jc6x-rj79-w4mx

Published

Jul 8, 2026

Updated

Oct 28, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 29, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

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-2026-54773.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs31th percentile — riskier than 31% of all scored CVEsHighest risk

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

How urgent is this, really

Where this sits among everything scored

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

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.

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.

Patches

Fixed in CoreWCF v1.8.1 and v1.9.1

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).

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-2026-54773 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 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. #### 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 con