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CVE-2021-23663

Status: ModifiedCritical (9.8)—
Severity9.8Critical · CVSS 3.1
Exploitation probability1.21 %higher than 68% of CVEs
Active exploitationNonot in the CISA catalog
Public exploitNot knownno public code found

All versions of package sey are vulnerable to Prototype Pollution via the deepmerge() function.

CVSS

Base score
9.8
Version
3.1
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days
1.21 %
Percentile among all scored CVEs
68
Score date
10/24/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (1)

SEY Project — SEY

CWEs

References

Show 2 references

Raw JSON (NVD)

Show
{
  "id": "CVE-2021-23663",
  "cveTags": [],
  "metrics": {
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        "source": "nvd@nist.gov",
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          "vectorString": "AV:N/AC:L/Au:N/C:P/I:P/A:P",
          "authentication": "NONE",
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    "cvssMetricV31": [
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          "product": "sey",
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  ],
  "published": "2021-12-10T20:15:08.453",
  "references": [
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      "url": "https://snyk.io/vuln/SNYK-JS-SEY-1727592",
      "tags": [
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        "Mitigation",
        "Third Party Advisory"
      ],
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    },
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      "url": "https://snyk.io/vuln/SNYK-JS-SEY-1727592",
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
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  "vulnStatus": "Modified",
  "weaknesses": [
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      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-1321"
        }
      ]
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  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "All versions of package sey are vulnerable to Prototype Pollution via the deepmerge() function."
    },
    {
      "lang": "es",
      "value": "Todas las versiones del paquete sey son vulnerables a una Contaminación de Prototipos por medio de la función deepmerge()"
    }
  ],
  "lastModified": "2026-06-17T03:38:51.350",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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          "operator": "OR"
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  "sourceIdentifier": "report@snyk.io"
}