Vulnerability Description
jq is a command-line JSON processor. In commits after 69785bf77f86e2ea1b4a20ca86775916889e91c9, 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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Jqlang | Jq | >= 2026-04-02, < 2026-04-08 |
Related Weaknesses (CWE)
References
- https://github.com/jqlang/jq/commit/fdf8ef0f0810e3d365cdd5160de43db46f57ed03Patch
- https://github.com/jqlang/jq/security/advisories/GHSA-6gc3-3g9p-xx28ExploitVendor Advisory
- https://github.com/jqlang/jq/security/advisories/GHSA-6gc3-3g9p-xx28ExploitVendor Advisory
FAQ
What is CVE-2026-39956?
CVE-2026-39956 is a vulnerability with a CVSS score of 6.1 (MEDIUM). jq is a command-line JSON processor. In commits after 69785bf77f86e2ea1b4a20ca86775916889e91c9, the _strindices builtin in jq's src/builtin.c passes its arguments directly to jv_string_indexes() witho...
How severe is CVE-2026-39956?
CVE-2026-39956 has been rated MEDIUM with a CVSS base score of 6.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-39956?
Check the references section above for vendor advisories and patch information. Affected products include: Jqlang Jq.