CVE-2021-42836: GJSON before 1.9.3 allows a ReDoS (regular expression denial of service) attack.

Q: How do I fix CVE-2021-42836?

gjson: upgrade to 1.9.3. Exact commands for each OS are on this page.

Q: Is CVE-2021-42836 being exploited?

CVE-2021-42836 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-42836 affect?

CVE-2021-42836 affects gjson. Severity is high (CVSS 7.5). GJSON before 1.9.3 allows a ReDoS (regular expression denial of service) attack.

Q: How urgent is CVE-2021-42836?

Priority 57/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADE

CVE-2021-42836 is a high-severity flaw (CVSS 7.5) affecting gjson. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

GJSON before 1.9.3 allows a ReDoS (regular expression denial of service) attack.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.4% (top 16%)
CISA exploited list	No
Weakness	CWE-400
Published	2021-10-22
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: gjson project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-10-22 18:15 UTCPublished CVE record published
2026-06-17 04:10 UTCUpdated Record last modified

gjson project gjson UPGRADE

Affected: < 1.9.3

Fixed in: 1.9.3

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 1.9.3 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade gjson

Note

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

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-2021-42836?

gjson: upgrade to 1.9.3. Exact commands for each OS are on this page.

Is CVE-2021-42836 being exploited?

CVE-2021-42836 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-2021-42836 affect?

CVE-2021-42836 affects gjson. Severity is high (CVSS 7.5). GJSON before 1.9.3 allows a ReDoS (regular expression denial of service) attack.

How urgent is CVE-2021-42836?

Priority 57/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2020-36067 HIGH 7.5 UPGRADE GJSON <=v1.6.5 allows attackers to cause a denial of service (panic: runtime error: slice bounds out of range)
CVE-2020-36066 HIGH 7.5 UPGRADE GJSON <1.6.5 allows attackers to cause a denial of service (remote) via crafted JSON.
CVE-2020-35380 HIGH 7.5 UPGRADE GJSON before 1.6.4 allows attackers to cause a denial of service via crafted JSON.

References

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