jqlang jq src/builtin.c jv_string_indexes out-of-bounds

Summaryinfo

A vulnerability was found in jqlang jq and classified as problematic. The affected element is the function jv_string_indexes of the file src/builtin.c. Such manipulation leads to out-of-bounds. This vulnerability is uniquely identified as CVE-2026-39956. Local access is required to approach this attack. No exploit exists. A patch should be applied to remediate this issue.

Detailsinfo

A vulnerability was found in jqlang jq (the affected version is unknown) and classified as problematic. Affected by this issue is the function jv_string_indexes of the file src/builtin.c. The manipulation with an unknown input leads to a out-of-bounds vulnerability. Using CWE to declare the problem leads to CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-39956 since 04/08/2026. The exploitation is known to be easy. Local access is required to approach this attack. Technical details are known, but there is no available exploit.

Applying the patch fdf8ef0f0810e3d365cdd5160de43db46f57ed03 is able to eliminate this problem. The bugfix is ready for download at github.com.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Vendor

• jqlang

Name

• jq

License

• open-source

Website

• Product: https://github.com/jqlang/jq/

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