Anchore's Quill is a tool designed to simplify macOS binary signing and notarization from any platform. Versions prior to 0.7.1 contain an SSRF vulnerability (CWE-918) that arises during the retrieval of Apple notarization submission logs. Specifically, Quill fetches URLs provided in Apple's notarization API responses without validating the URL scheme (e.g., enforcing HTTPS) or restricting the host to prevent local or multicast IP addresses. This lack of validation allows an attacker who can intercept or modify the API response to supply arbitrary URLs. When Quill follows these URLs, it can be coerced into making HTTP or HTTPS requests to attacker-controlled endpoints or internal network services. Exploitation requires the attacker to be able to tamper with Apple's notarization API responses, which is generally prevented by HTTPS with proper TLS certificate validation. However, environments employing TLS-intercepting proxies (common in corporate networks), compromised certificate authorities, or other trust boundary violations are vulnerable. The impact includes potential exfiltration of sensitive data such as cloud provider credentials or internal service responses accessible from the Quill client environment. Both the Quill CLI and library are affected, broadening the attack surface. The vulnerability was assigned CVE-2026-31959 and has a CVSS v3.1 score of 5.3, indicating medium severity. No known exploits in the wild have been reported. The issue is resolved in Quill version 0.7.1.

This SSRF vulnerability can lead to unauthorized internal network scanning and data exfiltration from systems running vulnerable versions of Quill. Organizations using Quill for macOS notarization in environments with TLS interception or compromised trust stores are at risk of attackers leveraging this flaw to access sensitive internal resources or credentials. The impact is primarily confidentiality loss, as attackers may retrieve sensitive data from internal services or cloud credentials. Integrity and availability impacts are minimal or not directly indicated. Because exploitation requires the ability to modify API responses, the attack complexity is high, limiting widespread exploitation under normal network conditions. However, in corporate or high-security environments where TLS interception proxies are common, the risk is elevated. The vulnerability affects both CLI users and automated systems using the Quill library, potentially impacting CI/CD pipelines and automated notarization workflows. Organizations relying on Quill for notarization processes may face operational risks if sensitive internal resources are exposed or credentials are compromised.

Upgrade all instances of Anchore Quill to version 0.7.1 or later, where this SSRF vulnerability is fixed. For environments where upgrading is not immediately possible, implement network-level controls to restrict outbound HTTP/HTTPS requests from systems running Quill to only trusted endpoints, preventing arbitrary URL access. Review and harden TLS interception proxies to ensure they do not improperly intercept or modify Apple's notarization API traffic. Validate and monitor certificate authorities in use to detect any compromise or unauthorized certificates. Employ network segmentation to limit access from notarization clients to sensitive internal resources. Additionally, consider implementing application-layer URL validation or sandboxing around Quill's network requests if custom modifications are feasible. Monitor logs for unusual outbound requests from Quill clients that could indicate exploitation attempts. Finally, educate security teams about the risk of SSRF in notarization tooling and incorporate this vulnerability into threat modeling and incident response plans.