Vulnerability-Lookup

CVE-2026-5501 (GCVE-0-2026-5501)

Vulnerability from cvelistv5 – Published: 2026-04-10 03:07 – Updated: 2026-04-22 13:59

Title

Improper Certificate Signature Verification in X.509 Chain Validation Allows Forged Leaf Certificates

Summary

wolfSSL_X509_verify_cert in the OpenSSL compatibility layer accepts a certificate chain in which the leaf's signature is not checked, if the attacker supplies an untrusted intermediate with Basic Constraints `CA:FALSE` that is legitimately signed by a trusted root. An attacker who obtains any leaf certificate from a trusted CA (e.g. a free DV cert from Let's Encrypt) can forge a certificate for any subject name with any public key and arbitrary signature bytes, and the function returns `WOLFSSL_SUCCESS` / `X509_V_OK`. The native wolfSSL TLS handshake path (`ProcessPeerCerts`) is not susceptible and the issue is limited to applications using the OpenSSL compatibility API directly, which would include integrations of wolfSSL into nginx and haproxy.

Severity

8.6 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

SSVC

Exploitation: none Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-04-22 03:55 UTC

CWE

CWE-295 - Improper certificate validation

Assigner

wolfSSL CNA under the icscert root

CNA scorecard B 80/100 over 51 records in the last 180 days details

References

1 reference

URL	Tags
https://github.com/wolfSSL/wolfssl/pull/10102

Impacted products

1 product

Vendor	Product	Version	CPE status
wolfSSL	wolfSSL	Affected: 0 , ≤ 5.9.0 (semver)	guessed

Credits

Calif.io in collaboration with Claude and Anthropic Research

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-5501

Vulnerability from fkie_nvd - Published: 2026-04-10 04:17 - Updated: 2026-06-17 10:59

Severity

8.1 (High) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Summary

References

	URL	Tags
	facts@wolfssl.com	https://github.com/wolfSSL/wolfssl/pull/10102	Issue Tracking

Impacted products

	Vendor	Product	Version
	wolfssl	wolfssl	*

JSON

To clipboard

{
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        {
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          ],
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    }
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          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "LOW",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "HIGH",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "facts@wolfssl.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-5501",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-04-22T03:55:48.544190Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-04-10T04:17:17.230",
  "references": [
    {
      "source": "facts@wolfssl.com",
      "tags": [
        "Issue Tracking"
      ],
      "url": "https://github.com/wolfSSL/wolfssl/pull/10102"
    }
  ],
  "sourceIdentifier": "facts@wolfssl.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-295"
        }
      ],
      "source": "facts@wolfssl.com",
      "type": "Secondary"
    }
  ]
}

GHSA-HG75-4CMP-F367

Vulnerability from github – Published: 2026-04-10 06:31 – Updated: 2026-04-27 18:32

Details

wolfSSL_X509_verify_cert in the OpenSSL compatibility layer accepts a certificate chain in which the leaf's signature is not checked, if the attacker supplies an untrusted intermediate with Basic Constraints CA:FALSE that is legitimately signed by a trusted root. An attacker who obtains any leaf certificate from a trusted CA (e.g. a free DV cert from Let's Encrypt) can forge a certificate for any subject name with any public key and arbitrary signature bytes, and the function returns WOLFSSL_SUCCESS / X509_V_OK. The native wolfSSL TLS handshake path (ProcessPeerCerts) is not susceptible and the issue is limited to applications using the OpenSSL compatibility API directly, which would include integrations of wolfSSL into nginx and haproxy.

Severity

8.1 (High)


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

8.6 (High)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-5501"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-04-10T04:17:17Z",
    "severity": "HIGH"
  },
  "details": "wolfSSL_X509_verify_cert in the OpenSSL compatibility layer accepts a certificate chain in which the leaf\u0027s signature is not checked, if the attacker supplies an untrusted intermediate with Basic Constraints `CA:FALSE` that is legitimately signed by a trusted root. An attacker who obtains any leaf certificate from a trusted CA (e.g. a free DV cert from Let\u0027s Encrypt) can forge a certificate for any subject name with any public key and arbitrary signature bytes, and the function returns `WOLFSSL_SUCCESS` / `X509_V_OK`. The native wolfSSL TLS handshake path (`ProcessPeerCerts`) is not susceptible and the issue is limited to applications using the OpenSSL compatibility API directly, which would include integrations of wolfSSL into nginx and haproxy.",
  "id": "GHSA-hg75-4cmp-f367",
  "modified": "2026-04-27T18:32:02Z",
  "published": "2026-04-10T06:31:38Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-5501"
    },
    {
      "type": "WEB",
      "url": "https://github.com/wolfSSL/wolfssl/pull/10102"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
      "type": "CVSS_V4"
    }
  ]
}

MSRC_CVE-2026-5501

Vulnerability from csaf_microsoft - Published: 2026-04-02 00:00 - Updated: 2026-04-15 01:02

Summary

Improper Certificate Signature Verification in X.509 Chain Validation Allows Forged Leaf Certificates

Scope

1 vulnerability in this advisory, including CVE-2026-5501.

CVE-2026-5501

Known not affected: 2 products

Open the full advisory

UBUNTU-CVE-2026-5501 (CVE-2026-5501)

Vulnerability from osv_ubuntu – Published: 2026-04-10 04:17 – Updated: 2026-10-17 09:37 – Source website

Details

wolfSSL_X509_verify_cert in the OpenSSL compatibility layer accepts a certificate chain in which the leaf's signature is not checked, if the attacker supplies an untrusted intermediate with Basic Constraints CA:FALSE that is legitimately signed by a trusted root. An attacker who obtains any leaf certificate from a trusted CA (e.g. a free DV cert from Let's Encrypt) can forge a certificate for any subject name with any public key and arbitrary signature bytes, and the function returns WOLFSSL_SUCCESS / X509_V_OK. The native wolfSSL TLS handshake path (ProcessPeerCerts) is not susceptible and the issue is limited to applications using the OpenSSL compatibility API directly, which would include integrations of wolfSSL into nginx and haproxy.

Severity

8.6 (High)


                    
                      CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

8.1 (High)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-5501	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-5501	REPORT
	https://github.com/wolfSSL/wolfssl/pull/10102	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libcyassl5",
            "binary_version": "3.4.8+dfsg-1"
          },
          {
            "binary_name": "libwolfssl0",
            "binary_version": "3.4.8+dfsg-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:16.04:LTS",
        "name": "wolfssl",
        "purl": "pkg:deb/ubuntu/wolfssl@3.4.8+dfsg-1?arch=source\u0026distro=xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.4.8+dfsg-1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libwolfssl15",
            "binary_version": "3.13.0+dfsg-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:18.04:LTS",
        "name": "wolfssl",
        "purl": "pkg:deb/ubuntu/wolfssl@3.13.0+dfsg-1?arch=source\u0026distro=bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.10.2+dfsg-2",
        "3.12.0+dfsg-1",
        "3.12.2+dfsg-1",
        "3.13.0+dfsg-1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libwolfssl24",
            "binary_version": "4.3.0+dfsg-2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "wolfssl",
        "purl": "pkg:deb/ubuntu/wolfssl@4.3.0+dfsg-2?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.1.0+dfsg-2",
        "4.2.0+dfsg-1",
        "4.2.0+dfsg-2",
        "4.2.0+dfsg-3",
        "4.3.0+dfsg-2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libwolfssl32",
            "binary_version": "5.2.0-2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "wolfssl",
        "purl": "pkg:deb/ubuntu/wolfssl@5.2.0-2?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.6.0-3",
        "5.0.0-1",
        "5.1.1-1",
        "5.2.0-1",
        "5.2.0-2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libwolfssl42t64",
            "binary_version": "5.6.6-1.3build1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "wolfssl",
        "purl": "pkg:deb/ubuntu/wolfssl@5.6.6-1.3build1?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "5.5.4-2",
        "5.5.4-2.1",
        "5.6.4-2",
        "5.6.6-1.2",
        "5.6.6-1.3",
        "5.6.6-1.3build1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libwolfssl42t64",
            "binary_version": "5.7.2-0.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:25.10",
        "name": "wolfssl",
        "purl": "pkg:deb/ubuntu/wolfssl@5.7.2-0.1?arch=source\u0026distro=questing"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "5.7.2-0.1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libwolfssl45",
            "binary_version": "5.9.2-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.10",
        "name": "wolfssl",
        "purl": "pkg:deb/ubuntu/wolfssl@5.9.2-1?arch=source\u0026distro=stonking"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "5.9.1-0.1",
        "5.9.2-1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libwolfssl44",
            "binary_version": "5.9.1-0.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "wolfssl",
        "purl": "pkg:deb/ubuntu/wolfssl@5.9.1-0.1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "5.7.2-0.1",
        "5.8.2-1.2",
        "5.8.4-1",
        "5.9.1-0.1"
      ]
    }
  ],
  "aliases": [],
  "details": "wolfSSL_X509_verify_cert in the OpenSSL compatibility layer accepts a certificate chain in which the leaf\u0027s signature is not checked, if the attacker supplies an untrusted intermediate with Basic Constraints `CA:FALSE` that is legitimately signed by a trusted root. An attacker who obtains any leaf certificate from a trusted CA (e.g. a free DV cert from Let\u0027s Encrypt) can forge a certificate for any subject name with any public key and arbitrary signature bytes, and the function returns `WOLFSSL_SUCCESS` / `X509_V_OK`. The native wolfSSL TLS handshake path (`ProcessPeerCerts`) is not susceptible and the issue is limited to applications using the OpenSSL compatibility API directly, which would include integrations of wolfSSL into nginx and haproxy.",
  "id": "UBUNTU-CVE-2026-5501",
  "modified": "2026-10-17T09:37:51Z",
  "published": "2026-04-10T04:17:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-5501"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-5501"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/wolfSSL/wolfssl/pull/10102"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    },
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-5501"
  ]
}

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.

Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

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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.
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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-5501 (GCVE-0-2026-5501)

FKIE_CVE-2026-5501

GHSA-HG75-4CMP-F367

MSRC_CVE-2026-5501

UBUNTU-CVE-2026-5501 (CVE-2026-5501)

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Nomenclature

Vulnerability timeline

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