Resource exhaustion in Fulcio - CVE-2025-66506
Published: December 16, 2025
Vulnerability identifier: #VU119999
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2025-66506
CWE-ID: CWE-400
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 perform a denial of service (DoS) attack.
The vulnerability exists due to application does not properly control consumption of internal resources within the identity.extractIssuerURL() function when parsing untrusted arguments. A remote attacker can pass a specially crafted request with a malicious OIDC identity token to trigger resource exhaustion and perform a denial of service (DoS) attack.
How to mitigate CVE-2025-66506
Install updates from vendor's website.