Vulnerability-Lookup

UBUNTU-CVE-2026-73253 (CVE-2026-73253)

Vulnerability from osv_ubuntu – Published: 2026-08-20 18:16 – Updated: 2026-08-20 18:16 – Source website

Details

Mongoose is an embedded web server and network library. Prior to version 7.22, an on-path network attacker with a wildcard certificate for a parent domain can impersonate deeper subdomains to a client using the built-in TLS stack. The mg_tls_verify_cert_san() and mg_tls_verify_cert_cn() functions in src/tls_builtin.c call mg_match(), whose wildcard can cross DNS label boundaries, so a pattern such as *.example.com can match foo.bar.example.com. The resulting hostname verification bypass permits interception and modification of TLS traffic. This issue is fixed in version 7.22.

Severity

9.1 (Critical)


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

9.1 (Critical)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-73253	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-73253	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "mongoose-webserver-source",
            "binary_version": "7.23+ds-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.10",
        "name": "mongoose",
        "purl": "pkg:deb/ubuntu/mongoose@7.23+ds-1?arch=source\u0026distro=stonking"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "7.21+ds-1",
        "7.21+ds-2",
        "7.22+ds-1",
        "7.23+ds-1"
      ]
    }
  ],
  "aliases": [],
  "details": "Mongoose is an embedded web server and network library. Prior to version 7.22, an on-path network attacker with a wildcard certificate for a parent domain can impersonate deeper subdomains to a client using the built-in TLS stack. The mg_tls_verify_cert_san() and mg_tls_verify_cert_cn() functions in src/tls_builtin.c call mg_match(), whose wildcard can cross DNS label boundaries, so a pattern such as *.example.com can match foo.bar.example.com. The resulting hostname verification bypass permits interception and modification of TLS traffic. This issue is fixed in version 7.22.",
  "id": "UBUNTU-CVE-2026-73253",
  "modified": "2026-08-20T18:16:00Z",
  "published": "2026-08-20T18:16:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-73253"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-73253"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/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:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-73253"
  ]
}

CVE-2026-73253 (GCVE-0-2026-73253)

Vulnerability from cvelistv5 – Published: 2026-08-20 17:41 – Updated: 2026-08-20 18:36

Title

Mongoose: TLS Hostname Verification Bypass via Overly Permissive Wildcard Matching

Summary

Severity

9.1 (Critical)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-20 18:33 UTC

CWE

CWE-295 - Improper Certificate Validation

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7639 records in the last 180 days details

References

4 references

URL	Tags
https://github.com/cesanta/mongoose/security/advi…	x_refsource_CONFIRM
https://github.com/cesanta/mongoose/pull/3611	x_refsource_MISC
https://github.com/cesanta/mongoose/commit/a9df52…	x_refsource_MISC
https://github.com/cesanta/mongoose/releases/tag/7.22	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
cesanta	mongoose	Affected: < 7.22

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-73253",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-20T18:33:38.834878Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-20T18:36:17.262Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/cesanta/mongoose/security/advisories/GHSA-jp6g-796f-39vp"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "mongoose",
          "vendor": "cesanta",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 7.22"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Mongoose is an embedded web server and network library. Prior to version 7.22, an on-path network attacker with a wildcard certificate for a parent domain can impersonate deeper subdomains to a client using the built-in TLS stack. The mg_tls_verify_cert_san() and mg_tls_verify_cert_cn() functions in src/tls_builtin.c call mg_match(), whose wildcard can cross DNS label boundaries, so a pattern such as *.example.com can match foo.bar.example.com. The resulting hostname verification bypass permits interception and modification of TLS traffic. This issue is fixed in version 7.22."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 9.1,
            "baseSeverity": "CRITICAL",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "HIGH",
            "vulnIntegrityImpact": "HIGH"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-295",
              "description": "CWE-295: Improper Certificate Validation",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-20T17:41:02.495Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/cesanta/mongoose/security/advisories/GHSA-jp6g-796f-39vp",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/cesanta/mongoose/security/advisories/GHSA-jp6g-796f-39vp"
        },
        {
          "name": "https://github.com/cesanta/mongoose/pull/3611",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/cesanta/mongoose/pull/3611"
        },
        {
          "name": "https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71"
        },
        {
          "name": "https://github.com/cesanta/mongoose/releases/tag/7.22",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/cesanta/mongoose/releases/tag/7.22"
        }
      ],
      "source": {
        "advisory": "GHSA-jp6g-796f-39vp",
        "discovery": "UNKNOWN"
      },
      "title": "Mongoose: TLS Hostname Verification Bypass via Overly Permissive Wildcard Matching"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-73253",
    "datePublished": "2026-08-20T17:41:02.495Z",
    "dateReserved": "2026-08-11T17:18:01.598Z",
    "dateUpdated": "2026-08-20T18:36:17.262Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

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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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UBUNTU-CVE-2026-73253 (CVE-2026-73253)

CVE-2026-73253 (GCVE-0-2026-73253)

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