CVE-2026-85471 in Quay
Summary
by MITRE • 10/12/2026
A flaw was found in Quay. An authenticated repository administrator could bypass the hostname blacklist in webhook notifications, leading to a Server-Side Request Forgery (SSRF) vulnerability. This allows the Quay application to be tricked into sending requests to internal network resources, such as cloud metadata services or other services within the cluster. Consequently, this could lead to the disclosure of sensitive information from these internal services.
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Analysis
by VulDB Data Team • 10/12/2026
The identified vulnerability in Quay represents a critical security flaw affecting authenticated repository administrators, specifically targeting the webhook notification mechanism. This issue stems from an insufficient validation process regarding hostname filtering during the construction and dispatch of HTTP requests triggered by webhook events. While Quay implements a blacklist-based approach to restrict outbound connections to potentially dangerous or internal addresses, this control was found to be bypassable through specific input manipulation techniques. The core technical flaw lies in the application's failure to strictly enforce domain resolution checks against the configured deny list before initiating network communication. By exploiting parsing ambiguities or encoding variations within the webhook URL configuration, an attacker can craft a request that circumvents the hostname blacklist logic. This allows the Quay server itself to act as a proxy, sending HTTP requests to arbitrary destinations defined by the attacker rather than being restricted solely to whitelisted external repositories or services.
This architectural weakness directly facilitates Server-Side Request Forgery (SSRF), a vulnerability class categorized under CWE-918 in industry standards such as MITRE's Common Weakness Enumeration. The operational impact of this flaw is severe, particularly within containerized environments where Quay is frequently deployed alongside other critical infrastructure components. An authenticated administrator can leverage the SSRF capability to probe internal network segments that are otherwise isolated from direct external access. A primary target for exploitation includes cloud metadata services, such as AWS Instance Metadata Service (IMDS) or Azure Managed Identity endpoints, which provide temporary credentials and configuration data to running instances. By directing Quay's outbound traffic toward these internal endpoints, an attacker can retrieve sensitive authentication tokens, IAM role assumptions, and other confidential instance-specific information without needing direct network connectivity to those services.
Furthermore, the implications extend beyond cloud metadata exposure. The vulnerability enables reconnaissance of internal cluster resources, including Kubernetes API servers, service meshes, and private database instances accessible only within the pod network or local host networking namespace. This capability aligns with ATT&CK technique T1598, specifically Phishing for Inbound Information, as it involves gathering data from internal systems to facilitate further lateral movement or privilege escalation. The disclosure of sensitive information obtained through these requests can lead to a complete compromise of the underlying infrastructure, allowing attackers to escalate privileges within the container orchestration platform or exfiltrate proprietary code and configuration secrets stored in private registries.
Mitigation strategies must prioritize immediate remediation at both the application level and the network perimeter. The most effective solution is for Quay maintainers to release an updated version that replaces the fragile blacklist approach with a strict allowlist mechanism, ensuring only explicitly approved domains can be contacted via webhooks. In environments where upgrading is not immediately feasible, administrators should implement robust network segmentation policies using Kubernetes Network Policies or cloud-native firewalls to restrict egress traffic from Quay pods. Specifically, outbound connections should be limited to known registry endpoints and blocked entirely for internal service CIDRs unless absolutely necessary. Additionally, deploying a reverse proxy with strict URL validation in front of the webhook endpoint can provide an additional layer of defense by inspecting and sanitizing request targets before they reach the application logic. Regular auditing of webhook configurations and limiting administrative privileges to only those users who strictly require such access are also recommended operational controls to reduce the attack surface associated with this vulnerability.