What is CVE-2025-66506?

CVE-2025-66506 is a high-severity vulnerability in Linuxfoundation Fulcio, classified under Asymmetric Resource Consumption (Amplification). CVSS score: 7.5/10. Published 2025-12-04.

How severe is CVE-2025-66506?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Linuxfoundation Fulcio

CVE-2025-66506

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 untru…

EPSS: 0.002 (9.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Linuxfoundation Fulcio
Sigstore Fulcio — versions < 1.8.3

Weakness classification (CWE)

CWE-405 — Asymmetric Resource Consumption (Amplification)

References

security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
security-advisories@github.com (Patch, x_refsource_MISC)

Frequently asked questions

What is CVE-2025-66506?: CVE-2025-66506 is a high-severity vulnerability in Linuxfoundation Fulcio, classified under Asymmetric Resource Consumption (Amplification). CVSS score: 7.5/10. Published 2025-12-04.
How severe is CVE-2025-66506?: High severity. CVSS v3 base score is 7.5 out of 10.