CVE-2025-66506
7.5 · HIGHOverview
CVE-2025-66506 is a high-severity vulnerability affecting linuxfoundation fulcio. It was published on December 4, 2025 and has a CVSS 3.1 base score of 7.5 (HIGH).
This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical Description
Fulcio is a free-to-use certificate authority for issuing code signing certificates for an OpenID Connect (OIDC) identity. Prior to 1.8.3, function identity.extractIssuerURL splits (via a call to strings.Split) its argument (which is untrusted data) on periods. As a result, in the face of a malicious request with an (invalid) OIDC identity token in the payload containing many period characters, a call to extractIssuerURL incurs allocations to the tune of O(n) bytes (where n stands for the length of the function's argument), with a constant factor of about 16. This vulnerability is fixed in 1.8.3.
Remediation
Check the references section for vendor advisories and patches from linuxfoundation. Update fulcio to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| linuxfoundation | fulcio | >= 0, < 1.8.3 | Affected |
Frequently Asked Questions
What is CVE-2025-66506?
CVE-2025-66506 is a high-severity vulnerability affecting linuxfoundation fulcio. It was published on December 4, 2025 and has a CVSS 3.1 base score of 7.5 (HIGH).
How severe is CVE-2025-66506?
This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2025-66506?
Check the references section for vendor advisories and patches from linuxfoundation. Update fulcio to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2025-66506?
CyberStrike's AI-powered security agents can automatically detect CVE-2025-66506 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
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