Common Weakness Enumeration

CWE-295

Allowed

Improper Certificate Validation

Abstraction: Base · Status: Draft

The product does not validate, or incorrectly validates, a certificate.

2039 vulnerabilities reference this CWE, most recent first.

GHSA-P3H6-32Q9-XWH5

Vulnerability from github – Published: 2023-08-11 06:30 – Updated: 2024-04-04 06:52
VLAI
Details

A vulnerability was discovered in Veritas NetBackup Snapshot Manager before 10.2.0.1 that allowed untrusted clients to interact with the RabbitMQ service. This was caused by improper validation of the client certificate due to misconfiguration of the RabbitMQ service. Exploiting this impacts the confidentiality and integrity of messages controlling the backup and restore jobs, and could result in the service becoming unavailable. This impacts only the jobs controlling the backup and restore activities, and does not allow access to (or deletion of) the backup snapshot data itself. This vulnerability is confined to the NetBackup Snapshot Manager feature and does not impact the RabbitMQ instance on the NetBackup primary servers.

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2023-40256"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2023-08-11T05:15:42Z",
    "severity": "CRITICAL"
  },
  "details": "A vulnerability was discovered in Veritas NetBackup Snapshot Manager before 10.2.0.1 that allowed untrusted clients to interact with the RabbitMQ service. This was caused by improper validation of the client certificate due to misconfiguration of the RabbitMQ service. Exploiting this impacts the confidentiality and integrity of messages controlling the backup and restore jobs, and could result in the service becoming unavailable. This impacts only the jobs controlling the backup and restore activities, and does not allow access to (or deletion of) the backup snapshot data itself. This vulnerability is confined to the NetBackup Snapshot Manager feature and does not impact the RabbitMQ instance on the NetBackup primary servers.",
  "id": "GHSA-p3h6-32q9-xwh5",
  "modified": "2024-04-04T06:52:16Z",
  "published": "2023-08-11T06:30:35Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2023-40256"
    },
    {
      "type": "WEB",
      "url": "https://www.veritas.com/content/support/en_US/security/VTS23-011"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-P3J9-QWH2-784J

Vulnerability from github – Published: 2022-03-11 00:02 – Updated: 2022-03-19 00:01
VLAI
Details

"Vault and Vault Enterprise 1.8.0 through 1.8.8, and 1.9.3 allowed the PKI secrets engine under certain configurations to issue wildcard certificates to authorized users for a specified domain, even if the PKI role policy attribute allow_subdomains is set to false. Fixed in Vault Enterprise 1.8.9 and 1.9.4.

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2022-25243"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2022-03-10T17:47:00Z",
    "severity": "MODERATE"
  },
  "details": "\"Vault and Vault Enterprise 1.8.0 through 1.8.8, and 1.9.3 allowed the PKI secrets engine under certain configurations to issue wildcard certificates to authorized users for a specified domain, even if the PKI role policy attribute allow_subdomains is set to false. Fixed in Vault Enterprise 1.8.9 and 1.9.4.",
  "id": "GHSA-p3j9-qwh2-784j",
  "modified": "2022-03-19T00:01:35Z",
  "published": "2022-03-11T00:02:08Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2022-25243"
    },
    {
      "type": "WEB",
      "url": "https://discuss.hashicorp.com"
    },
    {
      "type": "WEB",
      "url": "https://discuss.hashicorp.com/t/hcsec-2022-09-vault-pki-secrets-engine-policy-results-in-incorrect-wildcard-certificate-issuance/36600"
    },
    {
      "type": "WEB",
      "url": "https://security.gentoo.org/glsa/202207-01"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-P3WQ-V5CW-MP2F

Vulnerability from github – Published: 2022-05-17 02:30 – Updated: 2022-05-17 02:30
VLAI
Details

Microsoft Lync for Mac 2011 fails to properly validate certificates, allowing remote attackers to alter server-client communications, aka "Microsoft Lync for Mac Certificate Validation Vulnerability."

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2017-0129"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2017-03-17T00:59:00Z",
    "severity": "HIGH"
  },
  "details": "Microsoft Lync for Mac 2011 fails to properly validate certificates, allowing remote attackers to alter server-client communications, aka \"Microsoft Lync for Mac Certificate Validation Vulnerability.\"",
  "id": "GHSA-p3wq-v5cw-mp2f",
  "modified": "2022-05-17T02:30:43Z",
  "published": "2022-05-17T02:30:43Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2017-0129"
    },
    {
      "type": "WEB",
      "url": "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2017-0129"
    },
    {
      "type": "WEB",
      "url": "http://www.securityfocus.com/bid/96752"
    },
    {
      "type": "WEB",
      "url": "http://www.securitytracker.com/id/1038020"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-P3X8-4HX6-WG6W

Vulnerability from github – Published: 2022-05-14 02:57 – Updated: 2025-04-20 03:39
VLAI
Details

The "Middleton Community Bank Mobile Banking" by Middleton Community Bank app 3.0.0 -- aka middleton-community-bank-mobile-banking/id721843238 for iOS does not verify X.509 certificates from SSL servers, which allows man-in-the-middle attackers to spoof servers and obtain sensitive information via a crafted certificate.

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2017-9576"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2017-06-16T12:29:00Z",
    "severity": "MODERATE"
  },
  "details": "The \"Middleton Community Bank Mobile Banking\" by Middleton Community Bank app 3.0.0 -- aka middleton-community-bank-mobile-banking/id721843238 for iOS does not verify X.509 certificates from SSL servers, which allows man-in-the-middle attackers to spoof servers and obtain sensitive information via a crafted certificate.",
  "id": "GHSA-p3x8-4hx6-wg6w",
  "modified": "2025-04-20T03:39:12Z",
  "published": "2022-05-14T02:57:31Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2017-9576"
    },
    {
      "type": "WEB",
      "url": "https://medium.com/%40chronic_9612/advisory-44-credit-union-apps-for-ios-may-allow-login-credential-exposure-4d2f380b85c5"
    },
    {
      "type": "WEB",
      "url": "https://medium.com/@chronic_9612/advisory-44-credit-union-apps-for-ios-may-allow-login-credential-exposure-4d2f380b85c5"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-P3XV-97G8-4WMJ

Vulnerability from github – Published: 2022-05-17 04:52 – Updated: 2025-07-07 12:57
VLAI
Summary
Python Swift client is vulnerable to Missing SSL Certificate Check
Details

The OpenStack Python client library for Swift (python-swiftclient) from 1.0 before 2.0 does not verify X.509 certificates from SSL servers, which allows man-in-the-middle attackers to spoof servers and obtain sensitive information via a crafted certificate.

Show details on source website

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "python-swiftclient"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.0"
            },
            {
              "fixed": "2.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2013-6396"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2023-08-29T18:56:11Z",
    "nvd_published_at": "2014-02-18T19:55:00Z",
    "severity": "CRITICAL"
  },
  "details": "The OpenStack Python client library for Swift (python-swiftclient) from 1.0 before 2.0 does not verify X.509 certificates from SSL servers, which allows man-in-the-middle attackers to spoof servers and obtain sensitive information via a crafted certificate.",
  "id": "GHSA-p3xv-97g8-4wmj",
  "modified": "2025-07-07T12:57:06Z",
  "published": "2022-05-17T04:52:37Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2013-6396"
    },
    {
      "type": "WEB",
      "url": "https://github.com/openstack/python-swiftclient/commit/b182112719ab87942472e44aa3446ea0eb19a289"
    },
    {
      "type": "WEB",
      "url": "https://bugs.launchpad.net/python-swiftclient/+bug/1199783"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/chmouel/python-swiftclient"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/python-swiftclient/PYSEC-2014-12.yaml"
    },
    {
      "type": "WEB",
      "url": "https://review.opendev.org/c/openstack/python-swiftclient/+/69187"
    },
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2014/02/17/7"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Python Swift client is vulnerable to Missing SSL Certificate Check"
}

GHSA-P43H-5X4H-9PP7

Vulnerability from github – Published: 2022-05-24 17:18 – Updated: 2022-05-24 17:18
VLAI
Details

In GNOME glib-networking through 2.64.2, the implementation of GTlsClientConnection skips hostname verification of the server's TLS certificate if the application fails to specify the expected server identity. This is in contrast to its intended documented behavior, to fail the certificate verification. Applications that fail to provide the server identity, including Balsa before 2.5.11 and 2.6.x before 2.6.1, accept a TLS certificate if the certificate is valid for any host.

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2020-13645"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2020-05-28T12:15:00Z",
    "severity": "MODERATE"
  },
  "details": "In GNOME glib-networking through 2.64.2, the implementation of GTlsClientConnection skips hostname verification of the server\u0027s TLS certificate if the application fails to specify the expected server identity. This is in contrast to its intended documented behavior, to fail the certificate verification. Applications that fail to provide the server identity, including Balsa before 2.5.11 and 2.6.x before 2.6.1, accept a TLS certificate if the certificate is valid for any host.",
  "id": "GHSA-p43h-5x4h-9pp7",
  "modified": "2022-05-24T17:18:48Z",
  "published": "2022-05-24T17:18:48Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2020-13645"
    },
    {
      "type": "WEB",
      "url": "https://gitlab.gnome.org/GNOME/balsa/-/issues/34"
    },
    {
      "type": "WEB",
      "url": "https://gitlab.gnome.org/GNOME/glib-networking/-/issues/135"
    },
    {
      "type": "WEB",
      "url": "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/HLEX2IP62SU6WJ4SK3U766XGLQK3J62O"
    },
    {
      "type": "WEB",
      "url": "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/LRCUM22YEWWKNMN2BP5LTVDM5P4VWIXS"
    },
    {
      "type": "WEB",
      "url": "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TQEQJQ4XFMFCFJTEXKL2ZO3UELBPCKSK"
    },
    {
      "type": "WEB",
      "url": "https://security.gentoo.org/glsa/202007-50"
    },
    {
      "type": "WEB",
      "url": "https://security.netapp.com/advisory/ntap-20200608-0004"
    },
    {
      "type": "WEB",
      "url": "https://usn.ubuntu.com/4405-1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

GHSA-P4Q7-G7FF-823J

Vulnerability from github – Published: 2025-01-07 18:30 – Updated: 2025-11-04 00:32
VLAI
Details

When using Alt-Svc, ALPN did not properly validate certificates when the original server is redirecting to an insecure site. This vulnerability affects Firefox < 134 and Firefox ESR < 128.6.

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2025-0239"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-01-07T16:15:38Z",
    "severity": "MODERATE"
  },
  "details": "When using Alt-Svc, ALPN did not properly validate certificates when the original server is redirecting to an insecure site. This vulnerability affects Firefox \u003c 134 and Firefox ESR \u003c 128.6.",
  "id": "GHSA-p4q7-g7ff-823j",
  "modified": "2025-11-04T00:32:15Z",
  "published": "2025-01-07T18:30:49Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-0239"
    },
    {
      "type": "WEB",
      "url": "https://bugzilla.mozilla.org/show_bug.cgi?id=1929156"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/01/msg00004.html"
    },
    {
      "type": "WEB",
      "url": "https://www.mozilla.org/security/advisories/mfsa2025-01"
    },
    {
      "type": "WEB",
      "url": "https://www.mozilla.org/security/advisories/mfsa2025-02"
    },
    {
      "type": "WEB",
      "url": "https://www.mozilla.org/security/advisories/mfsa2025-04"
    },
    {
      "type": "WEB",
      "url": "https://www.mozilla.org/security/advisories/mfsa2025-05"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-P53G-MF4J-5XXX

Vulnerability from github – Published: 2022-05-24 16:45 – Updated: 2024-04-04 00:33
VLAI
Details

Citrix SD-WAN 10.2.x before 10.2.1 and NetScaler SD-WAN 10.0.x before 10.0.7 have Improper Certificate Validation.

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2019-11550"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2019-05-08T17:29:00Z",
    "severity": "MODERATE"
  },
  "details": "Citrix SD-WAN 10.2.x before 10.2.1 and NetScaler SD-WAN 10.0.x before 10.0.7 have Improper Certificate Validation.",
  "id": "GHSA-p53g-mf4j-5xxx",
  "modified": "2024-04-04T00:33:23Z",
  "published": "2022-05-24T16:45:20Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2019-11550"
    },
    {
      "type": "WEB",
      "url": "https://support.citrix.com/article/CTX247735"
    },
    {
      "type": "WEB",
      "url": "https://support.citrix.com/v1/search?searchQuery=%22%22\u0026lang=en\u0026sort=cr_date_desc\u0026prod=\u0026pver=\u0026ct=Security+Bulletin"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-P5J9-P2W8-Q5RW

Vulnerability from github – Published: 2026-08-03 15:32 – Updated: 2026-08-03 21:31
VLAI
Details

Net::SAML2 versions before 0.86 for Perl allow SAML authentication bypass by verifying responses against the response-embedded certificate in verify_xml when no trust anchor is configured.

verify_xml in Net::SAML2::Role::VerifyXML runs "return if !$anchors && !$cacert;" as soon as the XML::Sig check succeeds, and that check uses the X.509 certificate taken from the response's own dsig:KeyInfo/dsig:X509Certificate element, so an unanchored response is checked only against the key it carries. Binding::POST declares cacert as an optional Maybe[Str] with no default, so a POST binding built without one takes that path, and _verify_encrypted_assertion returns early the same way with "return $xml unless $cacert;".

Any caller that constructs Binding::POST or calls Assertion->new_from_xml without a cacert, cert_text, or anchors argument accepts a response signed by an attacker generated key whose self-signed certificate is embedded in that response, authenticating an arbitrary assertion.

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2026-18089"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-03T14:16:24Z",
    "severity": "HIGH"
  },
  "details": "Net::SAML2 versions before 0.86 for Perl allow SAML authentication bypass by verifying responses against the response-embedded certificate in verify_xml when no trust anchor is configured.\n\nverify_xml in Net::SAML2::Role::VerifyXML runs \"return if !$anchors \u0026\u0026 !$cacert;\" as soon as the XML::Sig check succeeds, and that check uses the X.509 certificate taken from the response\u0027s own dsig:KeyInfo/dsig:X509Certificate element, so an unanchored response is checked only against the key it carries. Binding::POST declares cacert as an optional Maybe[Str] with no default, so a POST binding built without one takes that path, and _verify_encrypted_assertion returns early the same way with \"return $xml unless $cacert;\".\n\nAny caller that constructs Binding::POST or calls Assertion-\u003enew_from_xml without a cacert, cert_text, or anchors argument accepts a response signed by an attacker generated key whose self-signed certificate is embedded in that response, authenticating an arbitrary assertion.",
  "id": "GHSA-p5j9-p2w8-q5rw",
  "modified": "2026-08-03T21:31:34Z",
  "published": "2026-08-03T15:32:47Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-18089"
    },
    {
      "type": "WEB",
      "url": "https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.85/source/lib/Net/SAML2/Binding/POST.pm#L21"
    },
    {
      "type": "WEB",
      "url": "https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.85/source/lib/Net/SAML2/Protocol/Assertion.pm#L84"
    },
    {
      "type": "WEB",
      "url": "https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.85/source/lib/Net/SAML2/Role/VerifyXML.pm#L32"
    },
    {
      "type": "WEB",
      "url": "https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.88/source/Changes"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-P5M6-F3FP-3V88

Vulnerability from github – Published: 2022-05-17 03:27 – Updated: 2022-05-17 03:27
VLAI
Details

The default configuration of Fortinet Fortigate UTM appliances uses the same Certification Authority certificate and same private key across different customers' installations, which makes it easier for man-in-the-middle attackers to spoof SSL servers by leveraging the presence of the Fortinet_CA_SSLProxy certificate in a list of trusted root certification authorities.

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2012-4948"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2012-11-14T12:30:00Z",
    "severity": "MODERATE"
  },
  "details": "The default configuration of Fortinet Fortigate UTM appliances uses the same Certification Authority certificate and same private key across different customers\u0027 installations, which makes it easier for man-in-the-middle attackers to spoof SSL servers by leveraging the presence of the Fortinet_CA_SSLProxy certificate in a list of trusted root certification authorities.",
  "id": "GHSA-p5m6-f3fp-3v88",
  "modified": "2022-05-17T03:27:30Z",
  "published": "2022-05-17T03:27:30Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2012-4948"
    },
    {
      "type": "WEB",
      "url": "http://osvdb.org/87048"
    },
    {
      "type": "WEB",
      "url": "http://www.kb.cert.org/vuls/id/111708"
    },
    {
      "type": "WEB",
      "url": "http://www.securityfocus.com/bid/56382"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

Mitigation
Architecture and Design Implementation

Certificates should be carefully managed and checked to assure that data are encrypted with the intended owner's public key.

Mitigation
Implementation

If certificate pinning is being used, ensure that all relevant properties of the certificate are fully validated before the certificate is pinned, including the hostname.

CAPEC-459: Creating a Rogue Certification Authority Certificate

An adversary exploits a weakness resulting from using a hashing algorithm with weak collision resistance to generate certificate signing requests (CSR) that contain collision blocks in their "to be signed" parts. The adversary submits one CSR to be signed by a trusted certificate authority then uses the signed blob to make a second certificate appear signed by said certificate authority. Due to the hash collision, both certificates, though different, hash to the same value and so the signed blob works just as well in the second certificate. The net effect is that the adversary's second X.509 certificate, which the Certification Authority has never seen, is now signed and validated by that Certification Authority.

CAPEC-475: Signature Spoofing by Improper Validation

An adversary exploits a cryptographic weakness in the signature verification algorithm implementation to generate a valid signature without knowing the key.