What’s Vulnerable › Vulnerabilities

CVE-2026-39956: jq: Missing runtime type checks for _strindices lead to crash and limited memory disclosure

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-04-13 · updated 2026-10-26
• Weakness: CWE-125

Description

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

How to fix

Upgrade to a fixed version: jqlang jq 2026-04-08. Check the vendor advisory for mitigations.

References

• https://github.com/jqlang/jq/commit/fdf8ef0f0810e3d365cdd5160de43db46f57ed03
• https://github.com/jqlang/jq/security/advisories/GHSA-6gc3-3g9p-xx28
• https://github.com/jqlang/jq/security/advisories/GHSA-6gc3-3g9p-xx28

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