CVE-2021-42836Public exploitNetwork attack vector

Application denial of service via unbounded matching

Published Oct 22, 2021 · Updated Aug 4, 2024

Regular expression denial of service in GJSON before 1.9.3 allows remote attackers to interrupt applications via crafted queries. The Get path passes wildcard keys and the % and !% query operators to unbounded match.Match calls, so adversarial patterns consume excessive CPU. Exploitation requires an application to pass attacker-controlled JSON or GJSON paths into Get; the resulting resource exhaustion stalls that process without affecting confidentiality or integrity.

CVSS severity7.5
High
EPSS probability2.42%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular expression denial of service in GJSON before 1.9.3 allows remote attackers to interrupt applications via crafted queries. The Get path passes wildcard keys and the % and !% query operators to unbounded match.Match calls, so adversarial patterns consume excessive CPU. Exploitation requires an application to pass attacker-controlled JSON or GJSON paths into Get; the resulting resource exhaustion stalls that process without affecting confidentiality or integrity.

The record

CVE
CVE-2021-42836
Published
Oct 22, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-400, CWE-697, CWE-1333, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 22, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
CWE-697Incorrect Comparison
CWE-1333Inefficient Regular Expression Complexity
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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