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CVE-2021-3377

Status: ModifiedMedium (6.1)—Exploit
Severity6.1Medium · CVSS 3.1
Exploitation probability8.00 %higher than 95% of CVEs
Active exploitationNonot in the CISA catalog
Public exploitAvailableNuclei template (automated mass detection)

The npm package ansi_up converts ANSI escape codes into HTML. In ansi_up v4, ANSI escape codes can be used to create HTML hyperlinks. Due to insufficient URL sanitization, this feature is affected by a cross-site scripting (XSS) vulnerability. This issue is fixed in v5.0.0.

CVSS

Base score
6.1
Version
3.1
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days
8.00 %
Percentile among all scored CVEs
95
Score date
10/21/2026

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).

Public exploits

Exploit code or detection templates are publicly available. This is not the same as confirmed active exploitation (KEV), but it raises the risk: patch with priority.

Affected technologies (1)

Ansi UP Project — Ansi UP

CWEs

References

Show 5 references

Raw JSON (NVD)

Show
{
  "id": "CVE-2021-3377",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
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        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
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          "baseScore": 4.3,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:M/Au:N/C:N/I:P/A:N",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "MEDIUM",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "NONE"
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        "acInsufInfo": false,
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          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "REQUIRED",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
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  "published": "2021-03-05T21:15:13.263",
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
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      "url": "https://security.netapp.com/advisory/ntap-20241108-0002/",
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-79"
        }
      ]
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  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "The npm package ansi_up converts ANSI escape codes into HTML. In ansi_up v4, ANSI escape codes can be used to create HTML hyperlinks. Due to insufficient URL sanitization, this feature is affected by a cross-site scripting (XSS) vulnerability. This issue is fixed in v5.0.0."
    },
    {
      "lang": "es",
      "value": "El paquete npm ansi_up convierte los códigos de escape ANSI en HTML. En ansi_up versión v4, los códigos de escape ANSI pueden ser usados para crear hipervínculos HTML. Debido a un saneamiento insuficiente de la URL, esta funcionalidad está afectada por una vulnerabilidad de tipo cross-site scripting (XSS). Este problema es corregido en versión v5.0.0"
    }
  ],
  "lastModified": "2026-06-17T04:05:00.207",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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        }
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  ],
  "sourceIdentifier": "cve@mitre.org"
}