What’s Vulnerable › Vulnerabilities

CVE-2026-81868: Steeltoe: Header-forwarded client cert lacks proof of private-key possession

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-17 · updated 2026-09-30
• Weakness: CWE-288

Description

Steeltoe is an open source project that provides a collection of libraries that helps users build cloud-native applications. Prior to 4.3.0, Steeltoe.Security.Authorization.Certificate deployments using AddOrgAndSpacePolicies() and UseCertificateAuthorization() trust the public certificate supplied in the X-Client-Cert request header without proving possession of the corresponding private key. Common Cloud Foundry routers do not remove this header from inbound requests. When inbound requests are not restricted to a known trusted proxy source IP, an attacker who obtains the public certificate of an application instance in the target organization or space and can reach the application can spoof X-Client-Cert to bypass the SameOrg and SameSpace policies for the certificate validity period. This issue is fixed in version 4.3.0.

Affected products

• SteeltoeOSS security-advisories: before 4.3.0

References

• https://github.com/SteeltoeOSS/Steeltoe/commit/b626ef3d60aaf19c68eeeed5ee81045406c8c6d0
• https://github.com/SteeltoeOSS/Steeltoe/releases/tag/4.3.0
• https://github.com/SteeltoeOSS/security-advisories/security/advisories/GHSA-5mq7-rwhj-4fh9

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