CVE-2026-39956: Jqlang Jq

Medium severity, CVSS 6.1. EPSS: 0.2% chance of exploitation in the next 30 days.

jq is a command-line JSON processor. Prior to version 1.8.2, the _strindices builtin in jq's src/builtin.c passes its arguments directly to jv_string_indexes() without verifying they are strings, and jv_string_indexes() in src/jv.c relies solely on assert() checks that are stripped in release builds compiled with -DNDEBUG. This allows an attacker to crash jq trivially with input like _strindices(0), and by crafting a numeric value whose IEEE-754 bit pattern maps to a chosen pointer, achieve a controlled pointer dereference and limited memory read/probe primitive. Any deployment that evaluates untrusted jq filters against a release build is vulnerable. This issue has been patched in commit fdf8ef0f0810e3d365cdd5160de43db46f57ed03, which is part of version 1.8.2.

Affected products

• Jqlang Jq: from 2026-04-02, before 2026-04-08 (fixed in 2026-04-08)

Published 2026-04-13. Last modified 2026-09-04.