Out-of-bounds Read in Jqlang Jq
CVE-2026-39956
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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H.
EPSS exploit prediction
EPSS: 0.002 (5.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 5th percentile — 5.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: -0.000
Affected products
- Jqlang Jq — versions >= 69785bf77f86e2ea1b4a20ca86775916889e91c9, < fdf8ef0f0810e3d365cdd5160de43db46f57ed03, < 1.8.2
Weakness classification (CWE)
References
- github.com/jqlang/jq/security/advisories/GHSA-6gc3-3g9p-xx28 (Exploit, Vendor Advisory)
- github.com/jqlang/jq/commit/fdf8ef0f0810e3d365cdd5160de43db46f57ed03 (Patch)
Frequently asked questions
- What is CVE-2026-39956?
- CVE-2026-39956 is a medium-severity vulnerability in Jqlang Jq, classified under Out-of-bounds Read. CVSS score: 6.1/10. Published 2026-04-13.
- How severe is CVE-2026-39956?
- Medium severity. CVSS v3 base score is 6.1 out of 10.