CVE-2026-40164

jq is a command-line JSON processor. Before commit 0c7d133c3c7e37c00b6d46b658a02244fdd3c784, jq used MurmurHash3 with a hardcoded, publicly visible seed (0x432A9843) for all JSON object hash table operations, which allowed an attacker to precompute key collisions offline. By supplying a crafted JSON object (~100 KB) where all keys hashed to the same bucket, hash table lookups degraded from O(1) to O(n), turning any jq expression into an O(n²) operation and causing significant CPU exhaustion. This affected common jq use cases such as CI/CD pipelines, web services, and data processing scripts, and was far more practical to exploit than existing heap overflow issues since it required only a small payload. This issue has been patched in commit 0c7d133c3c7e37c00b6d46b658a02244fdd3c784.

The vulnerability affects jq JSON processor versions prior to commit 0c7d133c3c7e37c00b6d46b658a02244fdd3c784 in the jqlang/jq repository. All production deployments using jq for processing untrusted JSON input are vulnerable, including installations via package managers (apt, yum, brew, chocolatey), containerized deployments, embedded jq libraries in web applications, and CI/CD pipeline integrations. The issue is present in the core jq codebase regardless of platform (Linux, macOS, Windows) or installation method. Vendor advisory available at https://github.com/jqlang/jq/security/advisories/GHSA-wwj8-gxm6-jc29 provides detailed technical analysis and confirmation of affected versions.