Vulnerability-Lookup

GHSA-F9FH-23QV-G394

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

Details

UltraVNC through 1.8.2.2 contains an out-of-bounds read in the wide-string to multibyte conversion helper. In rfb/dh.cpp:204, the vncWc2Mb() function passes a caller-supplied WCHAR pointer to wcslen() before any bounds check. If the caller provides a wide-character buffer that is not properly NUL-terminated, wcslen() reads past the end of the buffer until it encounters a NUL wchar, resulting in an out-of-bounds read. Under typical Win32 API usage this requires an abnormal caller contract. Impact is limited to a potential information disclosure from adjacent memory regions or a process crash (denial of service) if the over-read crosses a page boundary.

Severity

4.3 (Medium)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-44041"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-125"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-01T05:16:21Z",
    "severity": "MODERATE"
  },
  "details": "UltraVNC through 1.8.2.2 contains an out-of-bounds read in the wide-string to multibyte conversion helper. In rfb/dh.cpp:204, the vncWc2Mb() function passes a caller-supplied WCHAR pointer to wcslen() before any bounds check. If the caller provides a wide-character buffer that is not properly NUL-terminated, wcslen() reads past the end of the buffer until it encounters a NUL wchar, resulting in an out-of-bounds read. Under typical Win32 API usage this requires an abnormal caller contract. Impact is limited to a potential information disclosure from adjacent memory regions or a process crash (denial of service) if the over-read crosses a page boundary.",
  "id": "GHSA-f9fh-23qv-g394",
  "modified": "2026-07-01T06:31:34Z",
  "published": "2026-07-01T06:31:34Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44041"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ultravnc/UltraVNC"
    },
    {
      "type": "WEB",
      "url": "https://uvnc.com"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-44041 (GCVE-0-2026-44041)

Vulnerability from cvelistv5 – Published: 2026-07-01 03:33 – Updated: 2026-07-01 13:10

Title

UltraVNC vncWc2Mb calls wcslen() before validating that the wide string is NUL-terminated

Summary

Severity

4.3 (Medium)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-125 - Out-of-bounds Read

Assigner

securin

References

2 references

URL	Tags
https://uvnc.com/	vendor-advisory
https://github.com/ultravnc/UltraVNC	product

Impacted products

1 product

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

Credits

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

Show details on NVD website

JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-44041",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-01T13:10:10.152068Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-07-01T13:10:40.100Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "modules": [
            "winvnc",
            "vncviewer"
          ],
          "product": "UltraVNC",
          "vendor": "uvnc",
          "versions": [
            {
              "lessThanOrEqual": "1.8.2.2",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Arjun Basnet, Securin (arjun.basnet@securin.io)"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "UltraVNC through 1.8.2.2 contains an out-of-bounds read in the wide-string to multibyte conversion helper. In rfb/dh.cpp:204, the vncWc2Mb() function passes a caller-supplied WCHAR pointer to wcslen() before any bounds check. If the caller provides a wide-character buffer that is not properly NUL-terminated, wcslen() reads past the end of the buffer until it encounters a NUL wchar, resulting in an out-of-bounds read. Under typical Win32 API usage this requires an abnormal caller contract. Impact is limited to a potential information disclosure from adjacent memory regions or a process crash (denial of service) if the over-read crosses a page boundary."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 4.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-125",
              "description": "Out-of-bounds Read",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-01T03:33:19.127Z",
        "orgId": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
        "shortName": "securin"
      },
      "references": [
        {
          "name": "UltraVNC project page",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://uvnc.com/"
        },
        {
          "name": "UltraVNC source repository",
          "tags": [
            "product"
          ],
          "url": "https://github.com/ultravnc/UltraVNC"
        }
      ],
      "source": {
        "advisory": "Securin Security Advisory \u2014 FINDING-004",
        "discovery": "EXTERNAL"
      },
      "timeline": [
        {
          "lang": "en",
          "time": "2026-06-02T00:00:00.000Z",
          "value": "Vulnerability discovered during security audit"
        },
        {
          "lang": "en",
          "time": "2026-06-17T00:00:00.000Z",
          "value": "Reported to vendor (coordinated disclosure)"
        },
        {
          "lang": "en",
          "time": "2026-09-15T00:00:00.000Z",
          "value": "Planned public disclosure (90-day window)"
        }
      ],
      "title": "UltraVNC vncWc2Mb calls wcslen() before validating that the wide string is NUL-terminated"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
    "assignerShortName": "securin",
    "cveId": "CVE-2026-44041",
    "datePublished": "2026-07-01T03:33:19.127Z",
    "dateReserved": "2026-05-05T03:40:37.003Z",
    "dateUpdated": "2026-07-01T13:10:40.100Z",
    "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.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-F9FH-23QV-G394

CVE-2026-44041 (GCVE-0-2026-44041)

Tags

Sightings

Nomenclature