CVE-2026-54779 (CVSS 5.9)

Description

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.

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CVSS v3.1 Score

5.9

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS — Exploit Prediction

0.0027

Probability of exploitation

0.19%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-294 CWE-294

CWE-613 CWE-613

References

Other References

https://github.com/CoreWCF/CoreWCF/commit/3800c4e2bb4c6fde00ddacefdc2221ef33d55621 https://github.com/CoreWCF/CoreWCF/commit/7b0b5231cf21b4b5c1fc3caac9981f8bee43823f https://github.com/CoreWCF/CoreWCF/commit/84f8cff5a786b5aaa73448cb379d366a7df98238 https://github.com/CoreWCF/CoreWCF/releases/tag/v1.8.1 https://github.com/CoreWCF/CoreWCF/releases/tag/v1.9.1 https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-9jr3-rj99-8jq3

Frequently Asked Questions

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. It has a CVSS v3.1 base score of 5.9 (MEDIUM).

How severe is CVE-2026-54779? +

CVE-2026-54779 has a CVSS v3.1 score of 5.9 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0027, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-54779? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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