Vulnerability-Lookup

CVE-2021-4456 (GCVE-0-2021-4456)

Vulnerability from cvelistv5 – Published: 2026-02-27 00:16 – Updated: 2026-02-27 16:53

Title

Net::CIDR versions before 0.24 for Perl mishandle leading zeros in IP CIDR addresses, which may have unspecified impact

Summary

Net::CIDR versions before 0.24 for Perl mishandle leading zeros in IP CIDR addresses, which may have unspecified impact. The functions `addr2cidr` and `cidrlookup` may return leading zeros in a CIDR string, which may in turn be parsed as octal numbers by subsequent users. In some cases an attacker may be able to leverage this to bypass access controls based on IP addresses. The documentation advises validating untrusted CIDR strings with the `cidrvalidate` function. However, this mitigation is optional and not enforced by default. In practice, users may call `addr2cidr` or `cidrlookup` with untrusted input and without validation, incorrectly assuming that this is safe.

Severity ?

6.5 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

CWE

CWE-704 - Incorrect Type Conversion or Cast

Assigner

CPANSec

References

URL

Tags

	https://blog.urth.org/2021/03/29/security-issues-…	related
	https://github.com/svarshavchik/Net-CIDR/commit/e…	patch
	https://metacpan.org/dist/Net-CIDR/changes	release-notes

Impacted products

	Vendor	Product	Version
	MRSAM	Net::CIDR	Affected: 0 , < 0.24 (custom)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "LOW",
              "attackVector": "NETWORK",
              "availabilityImpact": "NONE",
              "baseScore": 6.5,
              "baseSeverity": "MEDIUM",
              "confidentialityImpact": "LOW",
              "integrityImpact": "LOW",
              "privilegesRequired": "NONE",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2021-4456",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-02-27T16:52:58.903437Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-02-27T16:53:23.671Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://cpan.org/modules",
          "defaultStatus": "unaffected",
          "packageName": "Net-CIDR",
          "product": "Net::CIDR",
          "programRoutines": [
            {
              "name": "addr2cidr"
            },
            {
              "name": "cidrlookup"
            }
          ],
          "repo": "https://github.com/svarshavchik/Net-CIDR",
          "vendor": "MRSAM",
          "versions": [
            {
              "lessThan": "0.24",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Net::CIDR versions before 0.24 for Perl mishandle leading zeros in IP CIDR addresses, which may have unspecified impact.\n\nThe functions `addr2cidr` and `cidrlookup` may return leading zeros in a CIDR string, which may in turn be parsed as octal numbers by subsequent users. In some cases an attacker may be able to leverage this to bypass access controls based on IP addresses.\n\nThe documentation advises validating untrusted CIDR strings with the `cidrvalidate` function. However, this mitigation is optional and not enforced by default. In practice, users may call `addr2cidr` or `cidrlookup` with untrusted input and without validation, incorrectly assuming that this is safe."
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-704",
              "description": "CWE-704 Incorrect Type Conversion or Cast",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-02-27T00:16:36.383Z",
        "orgId": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
        "shortName": "CPANSec"
      },
      "references": [
        {
          "tags": [
            "related"
          ],
          "url": "https://blog.urth.org/2021/03/29/security-issues-in-perl-ip-address-distros/"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/svarshavchik/Net-CIDR/commit/e3648c6bc6bdd018f90cca4149c467017d42bd10"
        },
        {
          "tags": [
            "release-notes"
          ],
          "url": "https://metacpan.org/dist/Net-CIDR/changes"
        }
      ],
      "solutions": [
        {
          "lang": "en",
          "value": "Use the `cidrvalidate` function on untrusted input before passing to the affected functions or upgrade to version 0.24 or later"
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "Net::CIDR versions before 0.24 for Perl mishandle leading zeros in IP CIDR addresses, which may have unspecified impact",
      "x_generator": {
        "engine": "cpansec-cna-tool 0.1"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
    "assignerShortName": "CPANSec",
    "cveId": "CVE-2021-4456",
    "datePublished": "2026-02-27T00:16:36.383Z",
    "dateReserved": "2025-05-18T22:36:11.463Z",
    "dateUpdated": "2026-02-27T16:53:23.671Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2021-4456\",\"sourceIdentifier\":\"9b29abf9-4ab0-4765-b253-1875cd9b441e\",\"published\":\"2026-02-27T01:16:13.553\",\"lastModified\":\"2026-02-27T17:16:19.903\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Net::CIDR versions before 0.24 for Perl mishandle leading zeros in IP CIDR addresses, which may have unspecified impact.\\n\\nThe functions `addr2cidr` and `cidrlookup` may return leading zeros in a CIDR string, which may in turn be parsed as octal numbers by subsequent users. In some cases an attacker may be able to leverage this to bypass access controls based on IP addresses.\\n\\nThe documentation advises validating untrusted CIDR strings with the `cidrvalidate` function. However, this mitigation is optional and not enforced by default. In practice, users may call `addr2cidr` or `cidrlookup` with untrusted input and without validation, incorrectly assuming that this is safe.\"},{\"lang\":\"es\",\"value\":\"Las versiones de Net::CIDR anteriores a la 0.24 para Perl manejan incorrectamente los ceros iniciales en las direcciones IP CIDR, lo que puede tener un impacto no especificado.\\n\\nLas funciones `addr2cidr` y `cidrlookup` pueden devolver ceros iniciales en una cadena CIDR, que a su vez pueden ser interpretados como n\u00fameros octales por usuarios posteriores. En algunos casos, un atacante podr\u00eda aprovechar esto para eludir los controles de acceso basados en direcciones IP.\\n\\nLa documentaci\u00f3n aconseja validar cadenas CIDR no confiables con la funci\u00f3n `cidrvalidate`. Sin embargo, esta mitigaci\u00f3n es opcional y no se aplica por defecto. En la pr\u00e1ctica, los usuarios pueden llamar a `addr2cidr` o `cidrlookup` con entrada no confiable y sin validaci\u00f3n, asumiendo incorrectamente que esto es seguro.\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N\",\"baseScore\":6.5,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"LOW\",\"integrityImpact\":\"LOW\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":3.9,\"impactScore\":2.5}]},\"weaknesses\":[{\"source\":\"9b29abf9-4ab0-4765-b253-1875cd9b441e\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-704\"}]}],\"references\":[{\"url\":\"https://blog.urth.org/2021/03/29/security-issues-in-perl-ip-address-distros/\",\"source\":\"9b29abf9-4ab0-4765-b253-1875cd9b441e\"},{\"url\":\"https://github.com/svarshavchik/Net-CIDR/commit/e3648c6bc6bdd018f90cca4149c467017d42bd10\",\"source\":\"9b29abf9-4ab0-4765-b253-1875cd9b441e\"},{\"url\":\"https://metacpan.org/dist/Net-CIDR/changes\",\"source\":\"9b29abf9-4ab0-4765-b253-1875cd9b441e\"}]}}",
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 6.5, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"MEDIUM\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N\", \"integrityImpact\": \"LOW\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"NONE\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"LOW\"}}, {\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2021-4456\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"poc\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-02-27T16:52:58.903437Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-02-27T16:44:01.688Z\"}}], \"cna\": {\"title\": \"Net::CIDR versions before 0.24 for Perl mishandle leading zeros in IP CIDR addresses, which may have unspecified impact\", \"source\": {\"discovery\": \"UNKNOWN\"}, \"affected\": [{\"repo\": \"https://github.com/svarshavchik/Net-CIDR\", \"vendor\": \"MRSAM\", \"product\": \"Net::CIDR\", \"versions\": [{\"status\": \"affected\", \"version\": \"0\", \"lessThan\": \"0.24\", \"versionType\": \"custom\"}], \"packageName\": \"Net-CIDR\", \"collectionURL\": \"https://cpan.org/modules\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"addr2cidr\"}, {\"name\": \"cidrlookup\"}]}], \"solutions\": [{\"lang\": \"en\", \"value\": \"Use the `cidrvalidate` function on untrusted input before passing to the affected functions or upgrade to version 0.24 or later\"}], \"references\": [{\"url\": \"https://blog.urth.org/2021/03/29/security-issues-in-perl-ip-address-distros/\", \"tags\": [\"related\"]}, {\"url\": \"https://github.com/svarshavchik/Net-CIDR/commit/e3648c6bc6bdd018f90cca4149c467017d42bd10\", \"tags\": [\"patch\"]}, {\"url\": \"https://metacpan.org/dist/Net-CIDR/changes\", \"tags\": [\"release-notes\"]}], \"x_generator\": {\"engine\": \"cpansec-cna-tool 0.1\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"Net::CIDR versions before 0.24 for Perl mishandle leading zeros in IP CIDR addresses, which may have unspecified impact.\\n\\nThe functions `addr2cidr` and `cidrlookup` may return leading zeros in a CIDR string, which may in turn be parsed as octal numbers by subsequent users. In some cases an attacker may be able to leverage this to bypass access controls based on IP addresses.\\n\\nThe documentation advises validating untrusted CIDR strings with the `cidrvalidate` function. However, this mitigation is optional and not enforced by default. In practice, users may call `addr2cidr` or `cidrlookup` with untrusted input and without validation, incorrectly assuming that this is safe.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-704\", \"description\": \"CWE-704 Incorrect Type Conversion or Cast\"}]}], \"providerMetadata\": {\"orgId\": \"9b29abf9-4ab0-4765-b253-1875cd9b441e\", \"shortName\": \"CPANSec\", \"dateUpdated\": \"2026-02-27T00:16:36.383Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-4456\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-02-27T16:53:23.671Z\", \"dateReserved\": \"2025-05-18T22:36:11.463Z\", \"assignerOrgId\": \"9b29abf9-4ab0-4765-b253-1875cd9b441e\", \"datePublished\": \"2026-02-27T00:16:36.383Z\", \"assignerShortName\": \"CPANSec\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}

FKIE_CVE-2021-4456

Vulnerability from fkie_nvd - Published: 2026-02-27 01:16 - Updated: 2026-02-27 17:16

Severity ?

6.5 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Summary

References

	URL	Tags
	9b29abf9-4ab0-4765-b253-1875cd9b441e	https://blog.urth.org/2021/03/29/security-issues-in-perl-ip-address-distros/
	9b29abf9-4ab0-4765-b253-1875cd9b441e	https://github.com/svarshavchik/Net-CIDR/commit/e3648c6bc6bdd018f90cca4149c467017d42bd10
	9b29abf9-4ab0-4765-b253-1875cd9b441e	https://metacpan.org/dist/Net-CIDR/changes

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Net::CIDR versions before 0.24 for Perl mishandle leading zeros in IP CIDR addresses, which may have unspecified impact.\n\nThe functions `addr2cidr` and `cidrlookup` may return leading zeros in a CIDR string, which may in turn be parsed as octal numbers by subsequent users. In some cases an attacker may be able to leverage this to bypass access controls based on IP addresses.\n\nThe documentation advises validating untrusted CIDR strings with the `cidrvalidate` function. However, this mitigation is optional and not enforced by default. In practice, users may call `addr2cidr` or `cidrlookup` with untrusted input and without validation, incorrectly assuming that this is safe."
    },
    {
      "lang": "es",
      "value": "Las versiones de Net::CIDR anteriores a la 0.24 para Perl manejan incorrectamente los ceros iniciales en las direcciones IP CIDR, lo que puede tener un impacto no especificado.\n\nLas funciones `addr2cidr` y `cidrlookup` pueden devolver ceros iniciales en una cadena CIDR, que a su vez pueden ser interpretados como n\u00fameros octales por usuarios posteriores. En algunos casos, un atacante podr\u00eda aprovechar esto para eludir los controles de acceso basados en direcciones IP.\n\nLa documentaci\u00f3n aconseja validar cadenas CIDR no confiables con la funci\u00f3n `cidrvalidate`. Sin embargo, esta mitigaci\u00f3n es opcional y no se aplica por defecto. En la pr\u00e1ctica, los usuarios pueden llamar a `addr2cidr` o `cidrlookup` con entrada no confiable y sin validaci\u00f3n, asumiendo incorrectamente que esto es seguro."
    }
  ],
  "id": "CVE-2021-4456",
  "lastModified": "2026-02-27T17:16:19.903",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 6.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 2.5,
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-02-27T01:16:13.553",
  "references": [
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "url": "https://blog.urth.org/2021/03/29/security-issues-in-perl-ip-address-distros/"
    },
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "url": "https://github.com/svarshavchik/Net-CIDR/commit/e3648c6bc6bdd018f90cca4149c467017d42bd10"
    },
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "url": "https://metacpan.org/dist/Net-CIDR/changes"
    }
  ],
  "sourceIdentifier": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-704"
        }
      ],
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "type": "Secondary"
    }
  ]
}

GHSA-6XJH-63FF-92MC

Vulnerability from github – Published: 2026-02-27 03:30 – Updated: 2026-02-27 18:31

Details

Net::CIDR versions before 0.24 for Perl mishandle leading zeros in IP CIDR addresses, which may have unspecified impact.

The functions addr2cidr and cidrlookup may return leading zeros in a CIDR string, which may in turn be parsed as octal numbers by subsequent users. In some cases an attacker may be able to leverage this to bypass access controls based on IP addresses.

The documentation advises validating untrusted CIDR strings with the cidrvalidate function. However, this mitigation is optional and not enforced by default. In practice, users may call addr2cidr or cidrlookup with untrusted input and without validation, incorrectly assuming that this is safe.

Severity ?

6.5 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2021-4456"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-704"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-02-27T01:16:13Z",
    "severity": "MODERATE"
  },
  "details": "Net::CIDR versions before 0.24 for Perl mishandle leading zeros in IP CIDR addresses, which may have unspecified impact.\n\nThe functions `addr2cidr` and `cidrlookup` may return leading zeros in a CIDR string, which may in turn be parsed as octal numbers by subsequent users. In some cases an attacker may be able to leverage this to bypass access controls based on IP addresses.\n\nThe documentation advises validating untrusted CIDR strings with the `cidrvalidate` function. However, this mitigation is optional and not enforced by default. In practice, users may call `addr2cidr` or `cidrlookup` with untrusted input and without validation, incorrectly assuming that this is safe.",
  "id": "GHSA-6xjh-63ff-92mc",
  "modified": "2026-02-27T18:31:05Z",
  "published": "2026-02-27T03:30:26Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-4456"
    },
    {
      "type": "WEB",
      "url": "https://github.com/svarshavchik/Net-CIDR/commit/e3648c6bc6bdd018f90cca4149c467017d42bd10"
    },
    {
      "type": "WEB",
      "url": "https://blog.urth.org/2021/03/29/security-issues-in-perl-ip-address-distros"
    },
    {
      "type": "WEB",
      "url": "https://metacpan.org/dist/Net-CIDR/changes"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ]
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2021-4456 (GCVE-0-2021-4456)

FKIE_CVE-2021-4456

GHSA-6XJH-63FF-92MC

Tags

Sightings

Nomenclature