CVE-2026-33228

See a problem?
Please try reporting it to the source first.
Source
https://cve.org/CVERecord?id=CVE-2026-33228
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33228.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-33228
Aliases
Downstream
Related
Published
2026-03-20T23:06:48.485Z
Modified
2026-07-08T07:28:27.013795836Z
Severity
  • 8.9 (High) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P CVSS Calculator
Summary
flatted: Prototype Pollution via parse()
Details

flatted is a circular JSON parser. Prior to version 3.4.2, the parse() function in flatted can use attacker-controlled string values from the parsed JSON as direct array index keys, without validating that they are numeric. Since the internal input buffer is a JavaScript Array, accessing it with the key "proto" returns Array.prototype via the inherited getter. This object is then treated as a legitimate parsed value and assigned as a property of the output object, effectively leaking a live reference to Array.prototype to the consumer. Any code that subsequently writes to that property will pollute the global prototype. This issue has been patched in version 3.4.2.

Database specific 
{
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33228.json",
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
        "CWE-1321"
    ]
}
References

Affected packages

Git / github.com/webreflection/flatted

Affected ranges

Type
GIT
Repo
https://github.com/webreflection/flatted
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
3bf09091c3562e17a0647bc06710dd6097079cf7
Fixed
885ddcc33cf9657caf38c57c7be45ae1c5272802
Database specific 
{
    "source": [
        "CPE_RANGE",
        "REFERENCES"
    ],
    "cpe": "cpe:2.3:a:webreflection:flatted:*:*:*:*:*:node.js:*:*",
    "extracted_events": [
        {
            "introduced": "0"
        },
        {
            "fixed": "3.4.2"
        }
    ]
}

Affected versions

v0.*
v0.1.0
v0.2.0
v0.2.1
v0.2.2
v0.2.3
v1.*
v1.0.0
v1.0.1
v1.0.2
v1.0.3
v2.*
v2.0.0
v2.0.1
v2.0.2
v3.*
v3.0.0
v3.0.1
v3.0.2
v3.0.3
v3.0.4
v3.0.5
v3.1.1
v3.2.0
v3.2.1
v3.2.10
v3.2.11
v3.2.12
v3.2.13
v3.2.2
v3.2.3
v3.2.4
v3.2.5
v3.2.6
v3.2.7
v3.2.8
v3.3.0
v3.3.1
v3.3.2
v3.3.3
v3.3.4
v3.4.0
v3.4.1

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33228.json"