How severe is CVE-2026-54780?

CVE-2026-54780 has a CVSS score of 3.7/10, rated LOW. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-54780?

CVE-2026-54780 affects the following packages: CoreWCF.Primitives (NuGet), CoreWCF.Primitives (NuGet). Ecosystems affected: NuGet.

How do I fix CVE-2026-54780?

Update CoreWCF.Primitives to 1.8.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54780 is resolved across your whole dependency graph.

How do I detect CVE-2026-54780 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-2026-54780 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-2026-54780 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-54780 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-2026-54780?

CVE-2026-54780 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 14th 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-2026-54780?

CVE-2026-54780 is classified as Broken Cryptographic Algorithm (CWE-327), CWE-757 (CWE-757). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-54780 published, and has it been updated?

CVE-2026-54780 was published on July 8, 2026 and was last updated on October 21, 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

LOW severity

CVE-2026-54780 — CoreWCF.Primitives

LOWFix: CoreWCF/CoreWCF@5874231

CVE-2026-54780 is a low-severity (CVSS 3.7) Broken Cryptographic Algorithm vulnerability in CoreWCF.Primitives. A fix is available for CoreWCF.Primitives — see the affected versions and patch details below.

CoreWCF: WS-Security Reference DigestMethod Algorithm-Suite Bypass

Also known asGHSA-4v55-cpmv-3vcm

Published

Jul 8, 2026

Updated

Oct 21, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 22, 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-2026-54780.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs14th percentile — riskier than 14% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2026-54780 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 394,803 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

CoreWCF’s WS-Security 1.0 receive pipeline validates the SignatureMethod of an incoming ds:SignedInfo against the configured SecurityAlgorithmSuite, but does not validate the DigestMethod declared on each ds:Reference. As a result, a sender can populate ds:SignedInfo with SignatureMethod values the suite accepts (for example rsa-sha256 under Basic256Sha256) while declaring a per-reference DigestMethod the suite rejects (for example http://www.w3.org/2000/09/xmldsig#sha1). The signature is then verified where it permits SHA-1 digests, and the message is accepted.

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-2026-54780 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 CoreWCF’s WS-Security 1.0 receive pipeline validates the `SignatureMethod` of an incoming `ds:SignedInfo` against the configured `SecurityAlgorithmSuite`, but does not validate the `DigestMethod` declared on each `ds:Reference`. As a result, a sender can populate `ds:SignedInfo` with `SignatureMethod` values the suite accepts (for example rsa-sha256 under Basic256Sha256) while declaring a per-reference `DigestMethod` the suite rejects (for example http://www.w3.org/2000/09/xmldsig#sha1). The signature is then verified where it permits SHA-1 digests, and the message is accepted. ###