Vulnerability-Lookup

CVE-2026-7839 (GCVE-0-2026-7839)

Vulnerability from cvelistv5 – Published: 2026-07-01 03:33 – Updated: 2026-07-09 04:35

Title

UltraVNC repeater ships hardcoded default admin password allowing unauthenticated admin access

Summary

UltraVNC repeater through 1.8.2.2 initializes the HTTP administration server with a hardcoded default password. In repeater/webgui/settings.c:197, when settings2.txt is absent on first run the repeater writes the literal string "adminadmi2" as the admin password via strcpy_s(saved_password, 64, "adminadmi2"). The HTTP Basic-auth handler wi_decode_auth() checks this password without rate-limiting or lockout. Any remote attacker who can reach the repeater HTTP port (default TCP 80) can authenticate as administrator using the well-known default credential on a fresh or unmodified installation, gaining full control of the repeater configuration including allow/deny rules and session visibility.

Severity

9.1 (Critical)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-07-01 12:32 UTC

CWE

CWE-798 - Use of Hard-coded Credentials

Assigner

securin mitre root

References

3 references

URL	Tags
https://uvnc.com/	vendor-advisory
https://github.com/ultravnc/UltraVNC	product
https://www.securin.io/zero-days/cve-2026-7839-ha…

Impacted products

1 product

Vendor	Product	Version	CPE status
uvnc	UltraVNC	Affected: 0 , ≤ 1.8.2.2 (custom)	guessed

Credits

Arjun Basnet, Securin (arjun.basnet@securin.io)

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-7839

Vulnerability from fkie_nvd - Published: 2026-07-01 05:16 - Updated: 2026-07-09 06:16

Severity

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

Summary

References

URL	Tags
33c584b5-0579-4c06-b2a0-8d8329fcab9c	https://github.com/ultravnc/UltraVNC	Product
33c584b5-0579-4c06-b2a0-8d8329fcab9c	https://uvnc.com/	Product, Release Notes
33c584b5-0579-4c06-b2a0-8d8329fcab9c	https://www.securin.io/zero-days/cve-2026-7839-hardcoded-default-admin-password-adminadmi2-ultravnc-repeater

Impacted products

	Vendor	Product	Version
	uvnc	ultravnc	*

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "modules": [
            "repeater"
          ],
          "product": "UltraVNC",
          "vendor": "uvnc",
          "versions": [
            {
              "lessThanOrEqual": "1.8.2.2",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:uvnc:ultravnc:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "593F7EC1-0922-4652-817A-7D57A0F1210D",
              "versionEndIncluding": "1.8.2.2",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "UltraVNC repeater through 1.8.2.2 initializes the HTTP administration server with a hardcoded default password. In repeater/webgui/settings.c:197, when settings2.txt is absent on first run the repeater writes the literal string \"adminadmi2\" as the admin password via strcpy_s(saved_password, 64, \"adminadmi2\"). The HTTP Basic-auth handler wi_decode_auth() checks this password without rate-limiting or lockout. Any remote attacker who can reach the repeater HTTP port (default TCP 80) can authenticate as administrator using the well-known default credential on a fresh or unmodified installation, gaining full control of the repeater configuration including allow/deny rules and session visibility."
    }
  ],
  "id": "CVE-2026-7839",
  "lastModified": "2026-07-09T06:16:22.213",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 9.1,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
          "version": "3.1"
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        "impactScore": 5.2,
        "source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
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        "ssvcData": {
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          "options": [
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            },
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            },
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            }
          ],
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          "timestamp": "2026-07-01T12:32:28.823292Z",
          "version": "2.0.3"
        }
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  "references": [
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    }
  ],
  "sourceIdentifier": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
  "vulnStatus": "Modified",
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}

GHSA-H7CC-6WQ3-9H7X

Vulnerability from github – Published: 2026-07-01 06:31 – Updated: 2026-07-09 06:31

Details

Severity

9.1 (Critical)


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

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-7839"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-798"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-01T05:16:24Z",
    "severity": "CRITICAL"
  },
  "details": "UltraVNC repeater through 1.8.2.2 initializes the HTTP administration server with a hardcoded default password. In repeater/webgui/settings.c:197, when settings2.txt is absent on first run the repeater writes the literal string \"adminadmi2\" as the admin password via strcpy_s(saved_password, 64, \"adminadmi2\"). The HTTP Basic-auth handler wi_decode_auth() checks this password without rate-limiting or lockout. Any remote attacker who can reach the repeater HTTP port (default TCP 80) can authenticate as administrator using the well-known default credential on a fresh or unmodified installation, gaining full control of the repeater configuration including allow/deny rules and session visibility.",
  "id": "GHSA-h7cc-6wq3-9h7x",
  "modified": "2026-07-09T06:31:59Z",
  "published": "2026-07-01T06:31:34Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-7839"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ultravnc/UltraVNC"
    },
    {
      "type": "WEB",
      "url": "https://uvnc.com"
    },
    {
      "type": "WEB",
      "url": "https://www.securin.io/zero-days/cve-2026-7839-hardcoded-default-admin-password-adminadmi2-ultravnc-repeater"
    }
  ],
  "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"
    }
  ]
}

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.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

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-2026-7839 (GCVE-0-2026-7839)

FKIE_CVE-2026-7839

GHSA-H7CC-6WQ3-9H7X

Tags

Sightings

Nomenclature

Related by attack behaviour