CVE-2026-40164
Published: 14 April 2026
Summary
CVE-2026-40164 is a high-severity Use of Weak Hash (CWE-328) vulnerability. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 6.4th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SC-5 (Denial-of-service Protection) and SC-6 (Resource Availability).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Timely flaw remediation requires updating jq to commit 0c7d133c3c7e37c00b6d46b658a02244fdd3c784 or later to eliminate the hardcoded hash seed vulnerability enabling CPU exhaustion.
Denial-of-service protection implements controls to mitigate resource exhaustion attacks like the O(n²) degradation from hash collisions in crafted JSON inputs to jq.
Resource availability protections safeguard CPU resources against exhaustion caused by processing collision-crafted JSON objects in vulnerable jq versions.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The hash collision vulnerability enables crafted JSON input to cause CPU exhaustion and application unresponsiveness in jq, directly facilitating Endpoint Denial of Service via application exploitation.
NVD Description
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…
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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.
Deeper analysisAI
CVE-2026-40164 is a hash collision vulnerability in jq, a command-line JSON processor. Prior to commit 0c7d133c3c7e37c00b6d46b658a02244fdd3c784, jq employed MurmurHash3 with a hardcoded, publicly known seed value (0x432A9843) for JSON object hash table operations. This design flaw enabled attackers to precompute key collisions offline, causing all keys in a crafted JSON object to hash to the same bucket. As a result, hash table lookups degraded from average O(1) to O(n) performance, transforming typical jq expressions into O(n²) operations and leading to severe CPU exhaustion.
The vulnerability carries a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and is associated with CWE-328 (Reversible One-Way Hash) and CWE-407 (Inappropriate Time Handling, due to algorithmic complexity). Any remote attacker can exploit it without privileges or user interaction by providing a specially crafted JSON object of approximately 100 KB. Successful exploitation causes denial-of-service through resource exhaustion, impacting common jq deployments in CI/CD pipelines, web services, and data processing scripts; it is noted as more practical than prior heap overflow issues due to the small payload size.
The issue was addressed in jq commit 0c7d133c3c7e37c00b6d46b658a02244fdd3c784, which patches the hash collision weakness. Security practitioners should update to this commit or later versions, as detailed in the GitHub security advisory (GHSA-wwj8-gxm6-jc29) and the patching commit.
Details
- CWE(s)