CVE-2026-54773: Signature Bypass (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 WS-Security signature verification performs a document-wide ds:Signature lookup, allowing an unauthenticated remote attacker to place a SOAP header before wsse:Security and cause WSSecurityOneDotZeroReceiveSecurityHeader to verify an attacker-supplied signature instead of the security header signature. 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

0.0024

Probability of exploitation

0.15%

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-347 CWE-347

References

Other References

https://github.com/CoreWCF/CoreWCF/commit/0589692d4b9a41d21b34ac48281e95f6df7f4ce5 https://github.com/CoreWCF/CoreWCF/commit/30aef805270976c42477e3f2a05f4e563d86e247 https://github.com/CoreWCF/CoreWCF/commit/4618f24165ad018ad3ed2636bf8c3bc87d2a3be2 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-jc6x-rj79-w4mx

Frequently Asked Questions

What is CVE-2026-54773? +

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 WS-Security signature verification performs a document-wide ds:Signature lookup, allowing an unauthenticated remote attacker to place a SOAP header before wsse:Security and cause WSSecurityOneDotZeroReceiveSecurityHeader to verify an attacker-supplied signature instead of the security header signature. 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-2026-54773? +

CVE-2026-54773 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 0.0024, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-54773? +

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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