CVE-2026-31960: Quill Denial of Service Vulnerability

CVE-2026-31960 Overview

CVE-2026-31960 is a Resource Exhaustion vulnerability affecting Quill, a tool that provides simple macOS binary signing and notarization from any platform. Quill versions prior to v0.7.1 contain unbounded reads of HTTP response bodies during the Apple notarization process, which can lead to memory exhaustion and denial of service conditions.

Critical Impact

An attacker capable of intercepting or modifying API responses from Apple's notarization service can cause the Quill client to exhaust memory and crash, resulting in denial of service. The impact is limited to availability with no effect on confidentiality or integrity.

Affected Products

• Quill versions prior to v0.7.1
• Quill CLI when used for notarization operations
• Quill library when used for notarization operations

Discovery Timeline

• 2026-03-11 - CVE-2026-31960 published to NVD
• 2026-03-12 - Last updated in NVD database

Technical Details for CVE-2026-31960

Vulnerability Analysis

This vulnerability is classified under CWE-770 (Allocation of Resources Without Limits or Throttling). When Quill processes HTTP responses during the notarization workflow with Apple's services, it reads the entire response body into memory without implementing any size limits or bounds checking. This design flaw creates a condition where an attacker who can control or modify the response content can return an arbitrarily large payload, causing the Quill client to consume excessive memory.

The exploitation of this vulnerability requires the ability to modify API responses from Apple's notarization service. Under standard network conditions, this is not possible due to HTTPS with proper TLS certificate validation. However, certain environments present elevated risk, including corporate networks with TLS-intercepting proxies, systems with compromised certificate authorities, or other scenarios involving trust boundary violations.

Root Cause

The root cause stems from improper resource allocation handling within Quill's HTTP response processing logic. The application fails to implement appropriate bounds or limits when reading response bodies during notarization API interactions. This missing validation allows unbounded memory allocation based on attacker-controlled content length values.

Attack Vector

The attack vector requires adjacent network access with high attack complexity due to the prerequisite of being able to intercept and modify HTTPS traffic. This could be achieved in environments where:

• TLS-intercepting proxies are deployed (common in corporate networks)
• Certificate authority compromise has occurred
• Other trust boundary violations exist that allow man-in-the-middle positioning

An attacker in such a position would intercept the response from Apple's notarization service and replace it with an arbitrarily large payload. When Quill attempts to read this response without size validation, it allocates memory proportional to the malicious payload size, eventually exhausting available memory and causing the application to crash.

Detection Methods for CVE-2026-31960

Indicators of Compromise

• Unusual memory consumption patterns in Quill processes during notarization operations
• Quill application crashes with out-of-memory errors
• Abnormally large HTTP response sizes from notarization endpoints in network logs
• TLS interception alerts or certificate validation warnings during notarization

Detection Strategies

• Monitor memory usage of Quill processes for anomalous spikes during notarization workflows
• Implement network monitoring to detect unusually large response payloads from Apple notarization services
• Alert on repeated Quill process crashes or restarts during build/signing pipelines
• Review proxy logs for suspicious response sizes targeting notarization endpoints

Monitoring Recommendations

• Enable memory utilization alerting for systems running Quill notarization tasks
• Implement application crash monitoring and logging for CI/CD environments using Quill
• Audit network infrastructure for unauthorized TLS interception configurations
• Monitor certificate trust stores for unexpected changes or additions

How to Mitigate CVE-2026-31960

Immediate Actions Required

• Upgrade Quill to version 0.7.1 or later immediately
• Audit network infrastructure for TLS-intercepting proxies that could be leveraged for exploitation
• Review certificate authority trust configurations on systems running Quill
• Implement resource limits for Quill processes as a temporary safeguard

Patch Information

This vulnerability is fixed in Quill version 0.7.1. The patch implements proper bounds checking on HTTP response body reads during the notarization process. Users should upgrade to 0.7.1 or later to remediate this vulnerability. For detailed patch information, refer to the GitHub Security Advisory.

Workarounds

• Ensure Quill is only used in environments without TLS-intercepting proxies when possible
• Implement container or process-level memory limits to prevent system-wide impact from memory exhaustion
• Monitor notarization processes and implement automatic termination if memory usage exceeds expected thresholds
• Consider network segmentation to reduce the attack surface for potential man-in-the-middle scenarios

# Example: Running Quill with memory limits using ulimit (Linux/macOS)
# Limit memory to 2GB to prevent system-wide impact
ulimit -v 2097152
quill notarize your-app.dmg