Common Weakness Enumeration

CWE-295

Allowed

Improper Certificate Validation

Abstraction: Base · Status: Draft

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

1903 vulnerabilities reference this CWE, most recent first.

GHSA-X5F3-QMWJ-4F84

Vulnerability from github – Published: 2022-02-15 01:57 – Updated: 2023-10-02 11:32
VLAI
Summary
Authentication bypass by capture-replay in github.com/cosmos/ethermint
Details

Cosmos Network Ethermint <= v0.4.0 is affected by a cross-chain transaction replay vulnerability in the EVM module. Since ethermint uses the same chainIDEpoch and signature schemes with ethereum for compatibility, a verified signature in ethereum is still valid in ethermint with the same msg content and chainIDEpoch, which enables "cross-chain transaction replay" attack.

Specific Go Packages Affected

github.com/cosmos/ethermint/rpc/namespaces/eth

Show details on source website

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/cosmos/ethermint"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.4.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2021-25835"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-294",
      "CWE-295"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2021-05-12T21:11:09Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "Cosmos Network Ethermint \u003c= v0.4.0 is affected by a cross-chain transaction replay vulnerability in the EVM module. Since ethermint uses the same chainIDEpoch and signature schemes with ethereum for compatibility, a verified signature in ethereum is still valid in ethermint with the same msg content and chainIDEpoch, which enables \"cross-chain transaction replay\" attack.\n\n### Specific Go Packages Affected\ngithub.com/cosmos/ethermint/rpc/namespaces/eth",
  "id": "GHSA-x5f3-qmwj-4f84",
  "modified": "2023-10-02T11:32:33Z",
  "published": "2022-02-15T01:57:18Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-25835"
    },
    {
      "type": "WEB",
      "url": "https://github.com/cosmos/ethermint/issues/687"
    },
    {
      "type": "WEB",
      "url": "https://github.com/cosmos/ethermint/pull/692"
    },
    {
      "type": "WEB",
      "url": "https://github.com/cosmos/ethermint/releases/tag/v0.4.1"
    }
  ],
  "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"
    }
  ],
  "summary": "Authentication bypass by capture-replay in github.com/cosmos/ethermint"
}

GHSA-X5HG-X4GV-J98M

Vulnerability from github – Published: 2026-05-07 00:09 – Updated: 2026-05-07 00:09
VLAI
Summary
OpenSearch has ineffective TLS certificate hostname verification
Details

Description

A regression was introduced in OpenSearch 2.18.0 that caused the plugins.security.ssl.transport.enforce_hostname_verification setting to be ineffective. When this setting was enabled, OpenSearch did not verify that the hostname in a connecting node's TLS certificate matched the hostname of the connection. This could allow a node with a valid certificate (signed by the cluster's trusted CA) but an incorrect hostname SAN to join the cluster.

Impact

Clusters running affected versions with hostname verification enabled did not receive the expected protection from this setting. A node presenting a certificate signed by the cluster's trusted CA could join the cluster regardless of whether its hostname SAN matched. This regression does not affect certificate validation itself — only the additional hostname verification check.

Patches

This issue is fixed in OpenSearch 2.19.4 and 3.3.0.

Workarounds

Use more restrictive values for plugins.security.nodes_dn to limit which certificates are accepted for node-to-node communication.

Show details on source website

{
  "affected": [
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.opensearch.plugin:opensearch-security"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.18.0"
            },
            {
              "fixed": "2.19.4.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.opensearch.plugin:opensearch-security"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0.0"
            },
            {
              "fixed": "3.3.0.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-07T00:09:18Z",
    "nvd_published_at": null,
    "severity": "LOW"
  },
  "details": "### Description\n\nA regression was introduced in OpenSearch 2.18.0 that caused the `plugins.security.ssl.transport.enforce_hostname_verification` setting to be ineffective. When this setting was enabled, OpenSearch did not verify that the hostname in a connecting node\u0027s TLS certificate matched the hostname of the connection. This could allow a node with a valid certificate (signed by the cluster\u0027s trusted CA) but an incorrect hostname SAN to join the cluster.\n\n### Impact\n\nClusters running affected versions with hostname verification enabled did not receive the expected protection from this setting. A node presenting a certificate signed by the cluster\u0027s trusted CA could join the cluster regardless of whether its hostname SAN matched. This regression does not affect certificate validation itself \u2014 only the additional hostname verification check.\n\n### Patches\n\nThis issue is fixed in OpenSearch 2.19.4 and 3.3.0.\n\n### Workarounds\n\nUse more restrictive values for `plugins.security.nodes_dn` to limit which certificates are accepted for node-to-node communication.",
  "id": "GHSA-x5hg-x4gv-j98m",
  "modified": "2026-05-07T00:09:18Z",
  "published": "2026-05-07T00:09:18Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/opensearch-project/security/security/advisories/GHSA-x5hg-x4gv-j98m"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/opensearch-project/security"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "OpenSearch has ineffective TLS certificate hostname verification"
}

GHSA-X5PM-H33Q-CJRW

Vulnerability from github – Published: 2024-02-20 21:30 – Updated: 2024-08-15 21:37
VLAI
Summary
Improper Certificate Validation in apache airflow mongo hook
Details

When ssl was enabled for Mongo Hook, default settings included "allow_insecure" which caused that certificates were not validated. This was unexpected and undocumented. Users are recommended to upgrade to version 4.0.0, which fixes this issue.

Show details on source website

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "apache-airflow-providers-mongo"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.0.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2024-25141"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2024-02-21T02:27:37Z",
    "nvd_published_at": "2024-02-20T21:15:08Z",
    "severity": "CRITICAL"
  },
  "details": "When ssl\u00a0was enabled for Mongo Hook, default settings included \"allow_insecure\" which caused that certificates were not validated. This was unexpected and undocumented.\nUsers are recommended to upgrade to version 4.0.0, which fixes this issue.",
  "id": "GHSA-x5pm-h33q-cjrw",
  "modified": "2024-08-15T21:37:23Z",
  "published": "2024-02-20T21:30:26Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-25141"
    },
    {
      "type": "WEB",
      "url": "https://github.com/apache/airflow/pull/37214"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/apache/airflow"
    },
    {
      "type": "WEB",
      "url": "https://lists.apache.org/thread/sqgbfqngjmn45ommmrgj7hvs7fgspsgm"
    },
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2024/02/20/5"
    }
  ],
  "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"
    }
  ],
  "summary": "Improper Certificate Validation in apache airflow mongo hook"
}

GHSA-X5QP-6Q24-3MCQ

Vulnerability from github – Published: 2022-05-13 01:42 – Updated: 2022-05-13 01:42
VLAI
Details

An issue was discovered in heinekingmedia StashCat before 1.5.18 for Android. No certificate pinning is implemented; therefore the attacker could issue a certificate for the backend and the application would not notice it.

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2017-11132"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2017-08-01T14:29:00Z",
    "severity": "HIGH"
  },
  "details": "An issue was discovered in heinekingmedia StashCat before 1.5.18 for Android. No certificate pinning is implemented; therefore the attacker could issue a certificate for the backend and the application would not notice it.",
  "id": "GHSA-x5qp-6q24-3mcq",
  "modified": "2022-05-13T01:42:08Z",
  "published": "2022-05-13T01:42:08Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2017-11132"
    },
    {
      "type": "WEB",
      "url": "http://seclists.org/fulldisclosure/2017/Jul/90"
    }
  ],
  "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-X654-4WJH-74Q6

Vulnerability from github – Published: 2022-05-13 01:36 – Updated: 2024-01-30 22:46
VLAI
Summary
Jenkins SSH Build Agents Plugin did not verify host keys
Details

It was found that jenkins-ssh-slaves-plugin before version 1.15 did not perform host key verification, thereby enabling Man-in-the-Middle attacks.

Show details on source website

{
  "affected": [
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.jenkins-ci.plugins:ssh-slaves"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.15"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2017-2648"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2024-01-30T22:46:58Z",
    "nvd_published_at": "2018-07-27T20:29:00Z",
    "severity": "MODERATE"
  },
  "details": "It was found that jenkins-ssh-slaves-plugin before version 1.15 did not perform host key verification, thereby enabling Man-in-the-Middle attacks.",
  "id": "GHSA-x654-4wjh-74q6",
  "modified": "2024-01-30T22:46:58Z",
  "published": "2022-05-13T01:36:51Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2017-2648"
    },
    {
      "type": "WEB",
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2017-2648"
    },
    {
      "type": "WEB",
      "url": "https://jenkins.io/security/advisory/2017-03-20"
    },
    {
      "type": "WEB",
      "url": "http://www.securityfocus.com/bid/96985"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Jenkins SSH Build Agents Plugin did not verify host keys"
}

GHSA-X6R5-VXFG-GQ3V

Vulnerability from github – Published: 2022-05-24 16:50 – Updated: 2023-08-01 23:17
VLAI
Summary
Helm Improper Certificate Validation
Details

helm Before 2.7.2 is affected by: CWE-295: Improper Certificate Validation. The impact is: Unauthorized clients could connect to the server because self-signed client certs were aloowed. The component is: helm (many files updated, see https://github.com/helm/helm/pull/3152/files/1096813bf9a425e2aa4ac755b6c991b626dfab50). The attack vector is: A malicious client could connect to the server over the network. The fixed version is: 2.7.2.

Show details on source website

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "helm.sh/helm"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.7.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2019-1010275"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2023-08-01T23:17:41Z",
    "nvd_published_at": "2019-07-17T21:15:00Z",
    "severity": "CRITICAL"
  },
  "details": "helm Before 2.7.2 is affected by: CWE-295: Improper Certificate Validation. The impact is: Unauthorized clients could connect to the server because self-signed client certs were aloowed. The component is: helm (many files updated, see https://github.com/helm/helm/pull/3152/files/1096813bf9a425e2aa4ac755b6c991b626dfab50). The attack vector is: A malicious client could connect to the server over the network. The fixed version is: 2.7.2.",
  "id": "GHSA-x6r5-vxfg-gq3v",
  "modified": "2023-08-01T23:17:41Z",
  "published": "2022-05-24T16:50:33Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2019-1010275"
    },
    {
      "type": "WEB",
      "url": "https://github.com/helm/helm/pull/3152"
    },
    {
      "type": "WEB",
      "url": "https://github.com/helm/helm/pull/3152/files/1096813bf9a425e2aa4ac755b6c991b626dfab50"
    },
    {
      "type": "WEB",
      "url": "https://github.com/helm/helm/commit/1096813bf9a425e2aa4ac755b6c991b626dfab50"
    },
    {
      "type": "WEB",
      "url": "https://github.com/helm/helm/releases/tag/v2.7.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Helm Improper Certificate Validation"
}

GHSA-X77C-2RV5-HHQQ

Vulnerability from github – Published: 2022-05-13 01:36 – Updated: 2025-04-20 03:50
VLAI
Details

Flash Seats Mobile App for Android version 1.7.9 and earlier and for iOS version 1.9.51 and earlier fails to properly validate SSL certificates provided by HTTPS connections, which may enable an attacker to conduct man-in-the-middle (MITM) attacks.

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2017-3190"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2017-12-16T02:29:00Z",
    "severity": "HIGH"
  },
  "details": "Flash Seats Mobile App for Android version 1.7.9 and earlier and for iOS version 1.9.51 and earlier fails to properly validate SSL certificates provided by HTTPS connections, which may enable an attacker to conduct man-in-the-middle (MITM) attacks.",
  "id": "GHSA-x77c-2rv5-hhqq",
  "modified": "2025-04-20T03:50:04Z",
  "published": "2022-05-13T01:36:44Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2017-3190"
    },
    {
      "type": "WEB",
      "url": "https://www.kb.cert.org/vuls/id/247016"
    },
    {
      "type": "WEB",
      "url": "https://www.wilderssecurity.com/threads/flash-seats-mobile-app-for-ios-fails-to-validate-ssl-certificates.392553"
    },
    {
      "type": "WEB",
      "url": "http://www.securityfocus.com/bid/96719"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.0/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-X77J-46HJ-595V

Vulnerability from github – Published: 2024-01-19 21:30 – Updated: 2024-01-30 15:30
VLAI
Details

Cohesity DataProtect 6.8.1 and 6.6.0d was discovered to have a incorrect access control vulnerability due to a lack of TLS Certificate Validation.

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2023-33295"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-01-19T20:15:10Z",
    "severity": "MODERATE"
  },
  "details": "Cohesity DataProtect 6.8.1 and 6.6.0d was discovered to have a incorrect access control vulnerability due to a lack of TLS Certificate Validation.",
  "id": "GHSA-x77j-46hj-595v",
  "modified": "2024-01-30T15:30:21Z",
  "published": "2024-01-19T21:30:35Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2023-33295"
    },
    {
      "type": "WEB",
      "url": "https://cohesity.com"
    },
    {
      "type": "WEB",
      "url": "https://github.com/cohesity/SecAdvisory/blob/master/CVE-2023-33295.md"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-X7F3-R5XV-V2V6

Vulnerability from github – Published: 2022-05-17 03:57 – Updated: 2024-02-14 18:30
VLAI
Details

The Chase mobile banking application for Android does not verify that the server hostname matches a domain name in the subject's Common Name (CN) or subjectAltName field of the X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate, related to overriding the default X509TrustManager. NOTE: this vulnerability was fixed in the summer of 2012, but the version number was not changed or is not known.

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2012-5810"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2012-11-04T22:55:00Z",
    "severity": "MODERATE"
  },
  "details": "The Chase mobile banking application for Android does not verify that the server hostname matches a domain name in the subject\u0027s Common Name (CN) or subjectAltName field of the X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate, related to overriding the default X509TrustManager. NOTE: this vulnerability was fixed in the summer of 2012, but the version number was not changed or is not known.",
  "id": "GHSA-x7f3-r5xv-v2v6",
  "modified": "2024-02-14T18:30:24Z",
  "published": "2022-05-17T03:57:47Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2012-5810"
    },
    {
      "type": "WEB",
      "url": "https://docs.google.com/document/pub?id=1roBIeSJsYq3Ntpf6N0PIeeAAvu4ddn7mGo6Qb7aL7ew"
    },
    {
      "type": "WEB",
      "url": "http://www.cs.utexas.edu/~shmat/shmat_ccs12.pdf"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-X8CH-H5VV-Q6CM

Vulnerability from github – Published: 2025-05-28 09:31 – Updated: 2025-05-30 18:31
VLAI
Details

libcurl supports pinning of the server certificate public key for HTTPS transfers. Due to an omission, this check is not performed when connecting with QUIC for HTTP/3, when the TLS backend is wolfSSL. Documentation says the option works with wolfSSL, failing to specify that it does not for QUIC and HTTP/3. Since pinning makes the transfer succeed if the pin is fine, users could unwittingly connect to an impostor server without noticing.

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2025-5025"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-05-28T07:15:24Z",
    "severity": "MODERATE"
  },
  "details": "libcurl supports *pinning* of the server certificate public key for HTTPS transfers. Due to an omission, this check is not performed when connecting with QUIC for HTTP/3, when the TLS backend is wolfSSL. Documentation says the option works with wolfSSL, failing to specify that it does not for QUIC and HTTP/3. Since pinning makes the transfer succeed if the pin is fine, users could unwittingly connect to an impostor server without noticing.",
  "id": "GHSA-x8ch-h5vv-q6cm",
  "modified": "2025-05-30T18:31:01Z",
  "published": "2025-05-28T09:31:26Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-5025"
    },
    {
      "type": "WEB",
      "url": "https://hackerone.com/reports/3153497"
    },
    {
      "type": "WEB",
      "url": "https://curl.se/docs/CVE-2025-5025.html"
    },
    {
      "type": "WEB",
      "url": "https://curl.se/docs/CVE-2025-5025.json"
    },
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2025/05/28/5"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ]
}

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.