CVE-2026-44041 (GCVE-0-2026-44041)
Vulnerability from cvelistv5 – Published: 2026-07-01 03:33 – Updated: 2026-07-09 04:36
VLAI
EPSS
VEX
Title
UltraVNC vncWc2Mb calls wcslen() before validating that the wide string is NUL-terminated
Summary
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)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-07-01 13:10 UTC
CWE
- CWE-125 - Out-of-bounds Read
Assigner
References
3 references
| URL | Tags |
|---|---|
| https://uvnc.com/ | vendor-advisory |
| https://github.com/ultravnc/UltraVNC | product |
| https://www.securin.io/zero-days/cve-2026-44041-v… |
Impacted products
{
"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": "2026-07-09T04:36:09.188Z",
"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"
},
{
"url": "https://www.securin.io/zero-days/cve-2026-44041-vncwc2mb-wcslen-before-bounds-check-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": "2026-07-09T04:36:09.188Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-44041",
"date": "2026-09-18",
"epss": "0.00413",
"percentile": "0.3528"
},
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"modules": [
"winvnc",
"vncviewer"
],
"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 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": "CVE-2026-44041",
"lastModified": "2026-07-09T06:16:21.010",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"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"
},
"exploitabilityScore": 2.8,
"impactScore": 1.4,
"source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
"type": "Secondary"
},
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "LOW",
"baseScore": 6.5,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "LOW",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L",
"version": "3.1"
},
"exploitabilityScore": 3.9,
"impactScore": 2.5,
"source": "nvd@nist.gov",
"type": "Primary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-44041",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-07-01T13:10:10.152068Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-07-01T05:16:21.033",
"references": [
{
"source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
"tags": [
"Product"
],
"url": "https://github.com/ultravnc/UltraVNC"
},
{
"source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
"tags": [
"Product",
"Release Notes"
],
"url": "https://uvnc.com/"
},
{
"source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
"url": "https://www.securin.io/zero-days/cve-2026-44041-vncwc2mb-wcslen-before-bounds-check-ultravnc"
}
],
"sourceIdentifier": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
"vulnStatus": "Modified",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-125"
}
],
"source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
"type": "Secondary"
}
]
}
},
"vulnrichment": {
"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": "2026-07-01T13:10:35.463Z",
"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": "2026-07-09T04:36:09.188Z",
"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"
},
{
"url": "https://www.securin.io/zero-days/cve-2026-44041-vncwc2mb-wcslen-before-bounds-check-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": "2026-07-09T04:36:09.188Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
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.
Loading…
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.
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.
Loading…
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.
Loading…