CVE-2026-15927
Description
A flaw was found in Red Hat Quay's repository-level mirror configuration feature. The POST and PUT handlers in endpoints/api/mirror.py accept an external_reference parameter without SSRF validation, unlike the organization-level mirror handlers which apply validate_external_registry_url(). A repository administrator can supply a crafted hostname that causes the Quay mirror worker to make requests via Skopeo to internal network services, cloud metadata endpoints, or other resources not intended to be reachable from the Quay application.
Statement
This Important flaw in Red Hat Quay's repository-level mirror configuration allows an authenticated repository administrator to conduct Server-Side Request Forgery (SSRF). By providing a specially crafted hostname, an attacker can force the Quay mirror worker to connect to internal network services or cloud metadata endpoints, potentially exposing sensitive internal resources. This risk is limited to actions performed by an authenticated administrator.
Mitigation
Restrict network egress from Quay mirror worker pods/containers using network
policies or firewall rules to block access to internal network ranges
(10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) and cloud metadata endpoints
(169.254.169.254, metadata.google.internal). Limit repository creation and
admin privileges to trusted users via Quay's RBAC configuration. If
repository-level mirroring is not required, disable the feature or restrict
access to the mirror API endpoints through a reverse proxy.
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 | 6.8 | N/A | 6.8 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | High | N/A | High |
| User Interaction | None | N/A | None |
| Scope | Changed | N/A | Changed |
| Confidentiality | High | N/A | High |
| Integrity Impact | None | N/A | None |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data
Integrity
Technical Impact: Execute Unauthorized Code or Commands
Access Control
Technical Impact: Bypass Protection Mechanism
By providing URLs to unexpected hosts or ports, attackers can make it appear that the server is sending the request, possibly bypassing access controls such as firewalls that prevent the attackers from accessing the URLs directly. The server can be used as a proxy to conduct port scanning of hosts in internal networks, use other URLs such as that can access documents on the system (using file://), or use other protocols such as gopher:// or tftp://, which may provide greater control over the contents of requests.
Acknowledgements
This issue was discovered by Martin Brodeur and Shaon Hossain (Red Hat).
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