CVE-2026-39956 jqlang CVE debrief

Who should care

Users of jq, especially those evaluating untrusted jq filters, should be aware of this vulnerability and take steps to mitigate it. Organizations using jq should prioritize updating to version 1.8.2 or later. Security teams should review compensating controls and monitor jq deployments for unusual activity. Affected operators and platforms should verify their jq versions and apply patches or mitigations as needed. This includes reviewing the current jq version in use, assessing the risk of exposure, and implementing necessary updates or mitigations.

Technical summary

The _strindices builtin in jq's src/builtin.c passes arguments directly to jv_string_indexes() without verifying they are strings. This allows crashes and potential controlled pointer dereferences. Patched in version 1.8.2. The vulnerability affects jq deployments that evaluate untrusted jq filters, especially those using release builds compiled with -DNDEBUG. Users should update to version 1.8.2 or later to mitigate this vulnerability. Affected deployments should verify their jq versions and apply patches or mitigations as needed.

Defensive priority

Organizations using jq should prioritize updating to version 1.8.2 or later to mitigate this vulnerability.

Recommended defensive actions

• Update jq to version 1.8.2 or later
• Restrict jq filter evaluations to trusted sources
• Monitor jq deployments for unusual activity
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE-2026-39956 vulnerability in jq allows an attacker to crash the processor and potentially achieve a controlled pointer dereference. The issue is patched in version 1.8.2. Evidence is based on official CVE and NVD records. Affected deployments should verify their jq versions and update to 1.8.2 or later. Defenders should review compensating controls and monitor for unusual activity. The CVE record was published on 2026-04-13T23:16:27.653Z and has not been modified since then.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.