What is CVE-2026-54779?

CVE-2026-54779 is a medium-severity vulnerability in Corewcf, classified under Authentication Bypass by Capture-replay. CVSS score: 5.9/10. Published 2026-07-08.

How severe is CVE-2026-54779?

Medium severity. CVSS v3 base score is 5.9 out of 10.

Vulnerability in Corewcf

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.

Published 2026-07-08 · last modified 2026-07-09.

CVSS v3 metric

CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N.

EPSS exploit prediction

EPSS: 0.004 (35.7th percentile), scored 2026-10-09.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 36th percentile — 35.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000

Affected products

Corewcf — versions >= 1.9.0, < 1.9.1, < 1.8.1

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-54779?: CVE-2026-54779 is a medium-severity vulnerability in Corewcf, classified under Authentication Bypass by Capture-replay. CVSS score: 5.9/10. Published 2026-07-08.
How severe is CVE-2026-54779?: Medium severity. CVSS v3 base score is 5.9 out of 10.