CVE-2026-40164 jq: Algorithmic complexity DoS via hardcoded MurmurHash3 seed
Attackers can cause CPU exhaustion in jq by submitting crafted JSON objects that exploit a hardcoded hash seed, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-40164?
CVE-2026-40164 is a high-severity denial of service vulnerability in jqlang jq, published on 13 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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 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.
Which versions are affected by CVE-2026-40164?
How do I fix CVE-2026-40164?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-40164 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40164 exists.
Sources
Also known as ALPINE-CVE-2026-40164, AZL-82934, BELL-CVE-2026-40164, DEBIAN-CVE-2026-40164, ECHO-472e-db5d-af63, GHSA-wwj8-gxm6-jc29.