CVE-2025-66506
Description
A flaw was found in Fulcio, a free-to-use certificate authority. This vulnerability allows a denial of service (DoS) due to excessive memory allocation when processing a malicious OpenID Connect (OIDC) identity token containing numerous period characters.
Statement
This vulnerability is rated Important for Red Hat as Fulcio, a certificate authority used for issuing code signing certificates, is susceptible to a denial of service when processing a specially crafted OpenID Connect (OIDC) token. This could lead to resource exhaustion and service unavailability in affected Red Hat products that utilize Fulcio.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Amplification; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
Sometimes this is a factor in "flood" attacks, but other types of amplification exist.
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