Vulnerability-Lookup

CVE-2026-19953 (GCVE-0-2026-19953)

Vulnerability from cvelistv5 – Published: 2026-08-31 17:29 – Updated: 2026-09-01 15:16

Title

URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep

Summary

URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep. nameprep lowercases each host label but performs no Unicode normalization. IDNA requires a label to be normalized to Form C before it is encoded (RFC 5891), so a label that is not already in NFC is encoded to a different A-label than its normalized form. A label built from the precomposed Devanagari sequence U+0958 U+093E encodes to xn--72b5c without normalization but to xn--11b2fg after NFC normalization, and xn--72b5c does not round-trip back to the original label. Any caller that reads host() from a URI built from untrusted input and uses it for a security decision (an allow or deny list, an SSRF filter, deduplication, a cache key) sees the non-standard label, while a client that fetches the same URL resolves the NFC form, so the check and the fetch can disagree about the host.

Severity

6.5 (Medium)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-01 15:16 UTC

CWE

CWE-1289 - Improper Validation of Unsafe Equivalence in Input

Assigner

CPANSec redhat root

References

5 references

URL	Tags
https://github.com/libwww-perl/URI/commit/956619a…	patch
https://github.com/libwww-perl/URI/pull/191	issue-tracking
https://metacpan.org/release/OALDERS/URI-5.36/changes	release-notes
https://www.rfc-editor.org/rfc/rfc5891#section-5.2	technical-description
http://www.openwall.com/lists/oss-security/2026/0…

Impacted products

1 product

Vendor	Product	Version	CPE status
		Affected: 0 , < 5.36 (custom)

Credits

Naseeb Dangi (naseeb0), Nankai University

Show details on NVD website

JSON

To clipboard

{
  "containers": {
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        "providerMetadata": {
          "dateUpdated": "2026-08-31T20:07:50.422Z",
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          {
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      },
      {
        "metrics": [
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              "confidentialityImpact": "LOW",
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              "userInteraction": "NONE",
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              "version": "3.1"
            }
          },
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            "other": {
              "content": {
                "id": "CVE-2026-19953",
                "options": [
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                    "Exploitation": "none"
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                  {
                    "Automatable": "yes"
                  },
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                  }
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                "role": "CISA Coordinator",
                "timestamp": "2026-09-01T15:16:46.820304Z",
                "version": "2.0.3"
              },
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          "shortName": "CISA-ADP"
        },
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      }
    ],
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          "defaultStatus": "unaffected",
          "modules": [
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          ],
          "packageName": "URI",
          "packageURL": "pkg:cpan/URI",
          "programFiles": [
            "lib/URI/_idna.pm"
          ],
          "programRoutines": [
            {
              "name": "URI::_idna::nameprep"
            }
          ],
          "repo": "https://github.com/libwww-perl/URI",
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            {
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              "version": "0",
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        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-1289",
              "description": "CWE-1289 Improper Validation of Unsafe Equivalence in Input",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
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        "orgId": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
        "shortName": "CPANSec"
      },
      "references": [
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/libwww-perl/URI/commit/956619a9e94f86d8d2c529b4e06a3674c54a73e7.patch"
        },
        {
          "tags": [
            "issue-tracking"
          ],
          "url": "https://github.com/libwww-perl/URI/pull/191"
        },
        {
          "tags": [
            "release-notes"
          ],
          "url": "https://metacpan.org/release/OALDERS/URI-5.36/changes"
        },
        {
          "tags": [
            "technical-description"
          ],
          "url": "https://www.rfc-editor.org/rfc/rfc5891#section-5.2"
        }
      ],
      "solutions": [
        {
          "lang": "en",
          "value": "Upgrade to URI 5.36 or later."
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
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    "assignerShortName": "CPANSec",
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    "datePublished": "2026-08-31T17:29:42.929Z",
    "dateReserved": "2026-08-15T21:13:08.480Z",
    "dateUpdated": "2026-09-01T15:16:50.672Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-19953",
      "date": "2026-09-15",
      "epss": "0.00373",
      "percentile": "0.30793"
    },
    "microsoft_vex": {
      "current_release_date": "2026-09-03T01:09:27.000Z",
      "cve": "CVE-2026-19953",
      "id": "msrc_CVE-2026-19953",
      "initial_release_date": "2026-09-03T01:09:27.000Z",
      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-19953.json",
      "version": "1"
    },
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    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-16T00:15:48Z",
      "cve": "CVE-2026-19953",
      "id": "CVE-2026-19953",
      "initial_release_date": "2026-09-02T01:07:08Z",
      "product_status:known_affected": "425",
      "product_status:recommended": "12",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-19953",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-19953.json",
      "version": "4"
    },
    "vulnrichment": {
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      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}

FKIE_CVE-2026-19953

Vulnerability from fkie_nvd - Published: 2026-08-31 18:17 - Updated: 2026-09-03 16:41

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://github.com/libwww-perl/URI/commit/956619a9e94f86d8d2c529b4e06a3674c54a73e7.patch
	9b29abf9-4ab0-4765-b253-1875cd9b441e	https://github.com/libwww-perl/URI/pull/191
	9b29abf9-4ab0-4765-b253-1875cd9b441e	https://metacpan.org/release/OALDERS/URI-5.36/changes
	9b29abf9-4ab0-4765-b253-1875cd9b441e	https://www.rfc-editor.org/rfc/rfc5891#section-5.2
	af854a3a-2127-422b-91ae-364da2661108	http://www.openwall.com/lists/oss-security/2026/08/31/14

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://cpan.org/modules",
          "defaultStatus": "unaffected",
          "modules": [
            "URI"
          ],
          "packageName": "URI",
          "packageURL": "pkg:cpan/URI",
          "programFiles": [
            "lib/URI/_idna.pm"
          ],
          "programRoutines": [
            {
              "name": "URI::_idna::nameprep"
            }
          ],
          "repo": "https://github.com/libwww-perl/URI",
          "versions": [
            {
              "lessThan": "5.36",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep.\n\nnameprep lowercases each host label but performs no Unicode normalization. IDNA requires a label to be normalized to Form C before it is encoded (RFC 5891), so a label that is not already in NFC is encoded to a different A-label than its normalized form. A label built from the precomposed Devanagari sequence U+0958 U+093E encodes to xn--72b5c without normalization but to xn--11b2fg after NFC normalization, and xn--72b5c does not round-trip back to the original label.\n\nAny caller that reads host() from a URI built from untrusted input and uses it for a security decision (an allow or deny list, an SSRF filter, deduplication, a cache key) sees the non-standard label, while a client that fetches the same URL resolves the NFC form, so the check and the fetch can disagree about the host."
    }
  ],
  "id": "CVE-2026-19953",
  "lastModified": "2026-09-03T16:41:09.297",
  "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"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-19953",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-09-01T15:16:46.820304Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-31T18:17:14.320",
  "references": [
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "url": "https://github.com/libwww-perl/URI/commit/956619a9e94f86d8d2c529b4e06a3674c54a73e7.patch"
    },
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "url": "https://github.com/libwww-perl/URI/pull/191"
    },
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "url": "https://metacpan.org/release/OALDERS/URI-5.36/changes"
    },
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "url": "https://www.rfc-editor.org/rfc/rfc5891#section-5.2"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "http://www.openwall.com/lists/oss-security/2026/08/31/14"
    }
  ],
  "sourceIdentifier": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-1289"
        }
      ],
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "type": "Secondary"
    }
  ]
}

GHSA-WF9V-63V3-FF2X

Vulnerability from github – Published: 2026-08-31 18:31 – Updated: 2026-09-01 18:30

Details

URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep.

nameprep lowercases each host label but performs no Unicode normalization. IDNA requires a label to be normalized to Form C before it is encoded (RFC 5891), so a label that is not already in NFC is encoded to a different A-label than its normalized form. A label built from the precomposed Devanagari sequence U+0958 U+093E encodes to xn--72b5c without normalization but to xn--11b2fg after NFC normalization, and xn--72b5c does not round-trip back to the original label.

Any caller that reads host() from a URI built from untrusted input and uses it for a security decision (an allow or deny list, an SSRF filter, deduplication, a cache key) sees the non-standard label, while a client that fetches the same URL resolves the NFC form, so the check and the fetch can disagree about the host.

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-2026-19953"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1289"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-31T18:17:14Z",
    "severity": "MODERATE"
  },
  "details": "URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep.\n\nnameprep lowercases each host label but performs no Unicode normalization. IDNA requires a label to be normalized to Form C before it is encoded (RFC 5891), so a label that is not already in NFC is encoded to a different A-label than its normalized form. A label built from the precomposed Devanagari sequence U+0958 U+093E encodes to xn--72b5c without normalization but to xn--11b2fg after NFC normalization, and xn--72b5c does not round-trip back to the original label.\n\nAny caller that reads host() from a URI built from untrusted input and uses it for a security decision (an allow or deny list, an SSRF filter, deduplication, a cache key) sees the non-standard label, while a client that fetches the same URL resolves the NFC form, so the check and the fetch can disagree about the host.",
  "id": "GHSA-wf9v-63v3-ff2x",
  "modified": "2026-09-01T18:30:35Z",
  "published": "2026-08-31T18:31:31Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-19953"
    },
    {
      "type": "WEB",
      "url": "https://github.com/libwww-perl/URI/pull/191"
    },
    {
      "type": "WEB",
      "url": "https://github.com/libwww-perl/URI/commit/956619a9e94f86d8d2c529b4e06a3674c54a73e7.patch"
    },
    {
      "type": "WEB",
      "url": "https://metacpan.org/release/OALDERS/URI-5.36/changes"
    },
    {
      "type": "WEB",
      "url": "https://www.rfc-editor.org/rfc/rfc5891#section-5.2"
    },
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2026/08/31/14"
    }
  ],
  "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"
    }
  ]
}

MSRC_CVE-2026-19953

Vulnerability from csaf_microsoft - Published: 2026-09-03 01:09 - Updated: 2026-09-03 01:09

Summary

URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep

Scope

1 vulnerability in this advisory, including CVE-2026-19953.

CVE-2026-19953

6.5 (Medium)


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

Known affected: 1 product

Open the full advisory

OPENSUSE-SU-2026:11663-1

Vulnerability from csaf_opensuse - Published: 2026-09-01 00:00 - Updated: 2026-09-01 00:00

Summary

perl-URI-5.360.0-1.1 on GA media

Severity

Moderate

Scope

1 vulnerability in this advisory, including CVE-2026-19953.

CVE-2026-19953

5.3 (Medium)


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

Recommended: 4 products

Open the full advisory

ubuntu-cve-2026-19953

Vulnerability from osv_ubuntu

Published

2026-08-31 18:17

Modified

2026-09-03 13:12

Summary

Details

Severity

6.5 (Medium)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-19953	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-19953	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "liburi-perl",
            "binary_version": "1.60-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:14.04:LTS",
        "name": "liburi-perl",
        "purl": "pkg:deb/ubuntu/liburi-perl@1.60-1?arch=source\u0026distro=trusty"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.60-1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "liburi-perl",
            "binary_version": "1.71-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:16.04:LTS",
        "name": "liburi-perl",
        "purl": "pkg:deb/ubuntu/liburi-perl@1.71-1?arch=source\u0026distro=xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.69-1",
        "1.71-1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "liburi-perl",
            "binary_version": "1.73-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:18.04:LTS",
        "name": "liburi-perl",
        "purl": "pkg:deb/ubuntu/liburi-perl@1.73-1?arch=source\u0026distro=bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.72-1",
        "1.72-2",
        "1.73-1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "liburi-perl",
            "binary_version": "1.76-2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "liburi-perl",
        "purl": "pkg:deb/ubuntu/liburi-perl@1.76-2?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.76-1",
        "1.76-2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "liburi-perl",
            "binary_version": "5.10-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "liburi-perl",
        "purl": "pkg:deb/ubuntu/liburi-perl@5.10-1?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "5.08-1",
        "5.10-1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "liburi-perl",
            "binary_version": "5.27-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "liburi-perl",
        "purl": "pkg:deb/ubuntu/liburi-perl@5.27-1?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "5.19-2",
        "5.21-1",
        "5.25-1",
        "5.27-1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "liburi-perl",
            "binary_version": "5.34-2build1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "liburi-perl",
        "purl": "pkg:deb/ubuntu/liburi-perl@5.34-2build1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "5.30-1",
        "5.34-2build1"
      ]
    }
  ],
  "aliases": [],
  "details": "URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep. nameprep lowercases each host label but performs no Unicode normalization. IDNA requires a label to be normalized to Form C before it is encoded (RFC 5891), so a label that is not already in NFC is encoded to a different A-label than its normalized form. A label built from the precomposed Devanagari sequence U+0958 U+093E encodes to xn--72b5c without normalization but to xn--11b2fg after NFC normalization, and xn--72b5c does not round-trip back to the original label. Any caller that reads host() from a URI built from untrusted input and uses it for a security decision (an allow or deny list, an SSRF filter, deduplication, a cache key) sees the non-standard label, while a client that fetches the same URL resolves the NFC form, so the check and the fetch can disagree about the host.",
  "id": "UBUNTU-CVE-2026-19953",
  "modified": "2026-09-03T13:12:10Z",
  "published": "2026-08-31T18:17:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-19953"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-19953"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-19953"
  ]
}

Sightings

Author	Source	Type	Date	Other

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

CVE-2026-19953 (GCVE-0-2026-19953)

FKIE_CVE-2026-19953

GHSA-WF9V-63V3-FF2X

MSRC_CVE-2026-19953

OPENSUSE-SU-2026:11663-1

ubuntu-cve-2026-19953

Vulnerability from osv_ubuntu

Tags

Sightings

Nomenclature