SB2026052728 - Multiple vulnerabilities in Fulcio

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Main Vulnerability Database SB2026052728

SB2026052728 - Multiple vulnerabilities in Fulcio

Published: May 27, 2026

Security Bulletin ID SB2026052728
CSH Severity
High
Patch available
YES
Number of vulnerabilities 3
Exploitation vector Remote access
Highest impact Data manipulation

Breakdown by Severity

High 100%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 3 vulnerabilities.


1) Server-Side Request Forgery (SSRF) (CVE-ID: N/A)

CWE-ID: CWE-918 - Server-Side Request Forgery (SSRF)

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:L/SI:N/SA:N/E:U/U:Amber


The vulnerability allows a remote attacker to cause server-side request forgery.

The vulnerability exists due to improper restriction of cross-host redirects in the OIDC discovery client when fetching OIDC discovery metadata. A remote attacker can return a redirect to a different host to cause server-side request forgery.


2) Insufficient verification of data authenticity (CVE-ID: N/A)

CWE-ID: CWE-345 - Insufficient Verification of Data Authenticity

CVSSv4: 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


The vulnerability allows a remote attacker to bypass signature verification integrity checks.

The vulnerability exists due to improper restriction of cross-host redirects in the OIDC discovery flow and verifier cache when processing a malicious jwks_uri. A remote attacker can return discovery metadata that points jwks_uri to an attacker-controlled host to bypass signature verification integrity checks.

The issue can poison the verifier cache with attacker-controlled verification keys.


3) Information disclosure (CVE-ID: N/A)

CWE-ID: CWE-200 - Exposure of sensitive information to an unauthorized actor

CVSSv4: 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


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 update from vendor's website.

References