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Fencer Vulns
medium 6.1

CVE-2026-39956 json

jq: Missing runtime type checks for _strindices lead to crash and limited memory disclosure

published 2026-04-13 6 mo ago modified 2026-10-26 13 d ago also EUVD-2026-22126

cvss
6.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 6%
public exploits
0
none known

Summary

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.

Patch / fix

  • jqlang jq 1.8.2
  • jq Debian 12 1.6-2.1+deb12u2
  • jq Debian 13 1.7.1-6+deb13u2
  • jq Debian 14 1.8.1-5

debian advisories DEBIAN-CVE-2026-39956

  • jq Ubuntu 22.04 LTS 1.6-2.1ubuntu3.2
  • jq Ubuntu 24.04 LTS 1.7.1-3ubuntu0.24.04.2
  • jq Ubuntu 25.10 1.8.1-3ubuntu1.1
  • jq Ubuntu 26.04 LTS 1.8.1-4ubuntu2
  • jq Ubuntu Pro 16.04 LTS 1.5+dfsg-1ubuntu0.1+esm4
  • jq Ubuntu Pro 18.04 LTS 1.5+dfsg-2ubuntu0.1~esm2
  • jq Ubuntu Pro 20.04 LTS 1.6-1ubuntu0.20.04.1+esm2

ubuntu advisories UBUNTU-CVE-2026-39956

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • jq hummingbird 1 1.8.1-3.hum1

red hat advisories RHSA-2026:8579

  • jq SLE Module for Basesystem 15 SP7, SLE Micro 5.5, SLE Micro 5.4 +1 more 1.6-150000.3.20.1
  • jq Linux Micro 6.0 1.6-6.1
  • jq SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 1.7.1-160000.3.1
  • jq Linux Micro 6.1 1.7.1-slfo.1.1_3.1

suse advisories SUSE-SU-2026:2983-1SUSE-SU-2026:22705-1SUSE-SU-2026:22545-1SUSE-SU-2026:22566-1SUSE-SU-2026:22664-1

  • jq openSUSE Leap 16.0 1.7.1-160000.3.1
  • jq openSUSE Tumbleweed 1.8.1-3.1

opensuse advisories openSUSE-SU-2026:21248-1openSUSE-SU-2026:10850-1

  • jq Alpine 3.24, Alpine 3.23, Alpine 3.22 1.8.2-r0

alpine advisories ALPINE-CVE-2026-39956

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • jq Azure Linux 3.0 1.7.1-5

azure linux advisories AZL-82973

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-39956 updated cvss 6.1

jq: missing runtime type checks for _strindices lead to crash and limited memory disclosure

  • Red Hat Ansible Automation Platform 2 automation-controller, ansible-automation-platform-26/hub-rhel9, ansible-automation-platform-26/controller-rhel9 Red Hat Ceph Storage 4 jq Red Hat Enterprise Linux 8 jq Red Hat Enterprise Linux 9 jq Red Hat Enterprise Linux 10 jq Red Hat OpenShift Container Platform 4 rhcos
    affected: workaround, no fix available “Do not use untrusted input as an argument to a jq builtin, specifically '_strindices'.”
  • Red Hat Hardened Images jq 1.8.1-3.hum1
    fixed: vendor fix “Do not use untrusted input as an argument to a jq builtin, specifically '_strindices'.” RHSA-2026:8579

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
6 mo ago

Exploit prediction

0.17% chance of exploitation in the next 30 days, higher than 6% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/jqlang/jq/security/advisories/GHSA-6gc3-3g9p-xx28 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.1 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H

Affected products

  • jqlang jq

Classification

Weakness
  • CWE-125 Out-of-bounds Read
  • CWE-476 NULL Pointer Dereference
  • CWE-843 Access of Resource Using Incompatible Type

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.