CVE-2026-31960 is a resource exhaustion vulnerability classified under CWE-770, affecting Anchore's Quill tool used for macOS binary signing and notarization. Prior to version 0.7.1, Quill performs unbounded reads of HTTP response bodies received from Apple's notarization service. Specifically, during the notarization process, Quill reads the entire HTTP response body into memory without imposing any size limits or throttling mechanisms. This behavior allows an attacker who can manipulate the notarization API responses to supply an arbitrarily large payload, causing Quill to consume excessive memory and ultimately crash due to resource exhaustion. Exploitation requires the ability to intercept and modify HTTPS traffic between Quill and Apple's notarization servers, which is normally prevented by 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 vulnerability affects both the Quill command-line interface and library components when used for notarization operations. The impact is limited to availability, with no confidentiality or integrity compromise. The vulnerability was publicly disclosed on March 11, 2026, and fixed in Quill version 0.7.1. No known exploits are reported in the wild.

The primary impact of CVE-2026-31960 is denial of service due to resource exhaustion. An attacker capable of manipulating notarization API responses can cause Quill to crash by forcing it to allocate excessive memory. This disrupts the notarization process, potentially delaying software release cycles or automated signing workflows that rely on Quill. Since Quill is used for macOS binary signing and notarization, organizations that integrate it into their CI/CD pipelines or build systems may experience operational downtime or failures. The vulnerability does not expose sensitive data nor allow code execution or data tampering, limiting its impact to availability. However, in environments where TLS interception or compromised trust exists, the risk of exploitation increases. Organizations relying heavily on Quill for notarization in such environments face increased risk of service disruption. The lack of known exploits reduces immediate threat but does not eliminate risk, especially in targeted attacks against software supply chains.

To mitigate CVE-2026-31960, organizations should upgrade Anchore Quill to version 0.7.1 or later, where the vulnerability is fixed by implementing limits on HTTP response body reads. For environments using TLS-intercepting proxies, ensure strict validation of TLS certificates and minimize trust boundary violations to prevent attackers from modifying notarization API responses. Network segmentation and monitoring should be employed to detect anomalous proxy behavior or certificate anomalies. Additionally, consider using endpoint security controls to detect and prevent memory exhaustion conditions. Where possible, avoid deploying Quill in environments with untrusted TLS interception. Implement logging and alerting on Quill failures to quickly identify potential exploitation attempts. Finally, review CI/CD and build pipeline security to reduce the risk of man-in-the-middle attacks on notarization traffic.