What is CVE-2026-54779?
CoreWCF is a port of the service side of Windows Communication Foundation (WCF) to .NET Core. Prior to 1.8.1 and 1.9.1, CoreWCF SAML token replay protection is inoperative because DefaultTokenReplayCache.TryAdd does not reject duplicate tokens when DetectReplayedTokens is enabled, allowing a captured token to be reused. This issue is fixed in versions 1.8.1 and 1.9.1.
The record classifies CVE-2026-54779 under weakness classes CWE-294, CWE-613. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on integrity. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 89 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 5.9 — MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N - EPSS (FIRST)
- 0.2% probability of exploitation in the next 30 days, higher than 18.4% of all scored CVEs
- CISA KEV
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Threadlinqs priority
- 3.7/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- Published
- 2026-07-08, last modified 2026-07-09
Is CVE-2026-54779 being exploited?
It currently carries a trending score of 34 in the Threadlinqs vulnerability feed.
Affected products and versions
- CoreWCF: CoreWCF
Affected software packages:
nuget:CoreWCF.Primitives— patched in 1.8.1nuget:CoreWCF.Primitives— patched in 1.9.1
How to fix CVE-2026-54779
Fixed versions are recorded for 2 packages: nuget:CoreWCF.Primitives 1.8.1, nuget:CoreWCF.Primitives 1.9.1. No vendor patch reference has been recorded for CVE-2026-54779 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.
Threat activity tracking CVE-2026-54779
No threat campaign in the Threadlinqs corpus currently references CVE-2026-54779, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.
Sources
Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.