Information disclosure in Fulcio - #VU132353
Published: May 27, 2026
Vulnerability identifier: #VU132353
CSH Severity: High
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Amber
CVE-ID: N/A
CWE-ID: CWE-200
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Sigstore
Affected software:
Fulcio
Fulcio
Detailed vulnerability description
The vulnerability allows a remote attacker to disclose sensitive information.
The vulnerability exists due to improper access control in the transport that attaches Kubernetes ServiceAccount tokens when sending OIDC discovery and JWKS requests. A remote attacker can trigger outbound requests to an external host to disclose sensitive information.
The leaked information is the in-cluster Kubernetes ServiceAccount token, including when redirects cross host boundaries or when a wildcard kubernetes MetaIssuer matches an external endpoint while a local Kubernetes issuer is configured.
Remediation
Install security update from vendor's website.