CVE-2026-39956: jq is a command-line JSON processor

Routine

MEDIUM 6.1UPGRADE

CVE-2026-39956 is a medium-severity flaw (CVSS 6.1) affecting jq. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.2% (top 93%)
CISA exploited list	No
Weakness	CWE-125, CWE-476, CWE-843
Published	2026-04-13
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: jqlang

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-13 23:16 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

jqlang jq UPGRADE

Affected: >= 2026-04-02 and < 2026-04-08

Fixed in: 2026-04-08

Safe to downgrade to: a release before 2026-04-02

1. Check installed version

apt-cache policy jq || rpm -q jq || jq --version

2. UPGRADE to 2026-04-08 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade jq

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade jq

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2026-04-02 (Debian / Ubuntu)

apt-cache madison jq sudo apt install jq=<VERSION_BEFORE_2026-04-02> sudo apt-mark hold jq

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list jq sudo dnf downgrade jq-<VERSION_BEFORE_2026-04-02> sudo dnf versionlock add jq

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-39956?

jq: upgrade to 2026-04-08. Exact commands for each OS are on this page.

Is CVE-2026-39956 being exploited?

CVE-2026-39956 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-39956 affect?

CVE-2026-39956 affects jq. Severity is medium (CVSS 6.1). 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 s

How urgent is CVE-2026-39956?

Priority 28/100. Public exploit reference

Related CVEs

CVE-2026-32316 HIGH 8.2 UPGRADE jq is a command-line JSON processor
CVE-2026-39979 MEDIUM 6.5 UPGRADE UPGRADE jq is a command-line JSON processor
CVE-2026-33948 MEDIUM 5.3 UPGRADE jq is a command-line JSON processor
CVE-2026-33947 MEDIUM 6.2 UPGRADE jq is a command-line JSON processor
CVE-2026-43894 MEDIUM 6.2 UPGRADE jq is a command-line JSON processor

References

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