CVE-2026-7831

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-7831", "assignerOrgId": "33c584b5-0579-4c06-b2a0-8d8329fcab9c", "state": "PUBLISHED", "assignerShortName": "securin", "dateReserved": "2026-05-05T04:03:22.622Z", "datePublished": "2026-07-01T03:33:25.314Z", "dateUpdated": "2026-07-09T04:35:54.891Z"}, "containers": {"cna": {"title": "UltraVNC viewer off-by-one stack overflow in ServerInit desktop name parsing", "descriptions": [{"lang": "en", "value": "UltraVNC viewer through 1.8.2.2 contains an off-by-one stack buffer overflow in the RFB ServerInit message handler. In vncviewer/ClientConnection.cpp, when the server-supplied nameLength equals exactly 2024 the code declares a 2024-byte stack buffer _dn[2024] and calls ReadString(_dn, 2024). ReadString writes the NUL terminator at buf[length], i.e., _dn[2024], one byte past the end of the stack buffer. A malicious VNC server can trigger this condition by advertising a desktop name of length 2024 in its ServerInit message. On release builds without stack canaries the single-byte NUL overwrite adjacent stack data. On builds with /GS stack protection the canary is corrupted and the process terminates, resulting in denial of service. User interaction (connecting the viewer to the malicious server) is required."}], "affected": [{"vendor": "uvnc", "product": "UltraVNC", "versions": [{"version": "0", "lessThanOrEqual": "1.8.2.2", "status": "affected", "versionType": "custom"}], "defaultStatus": "unaffected", "modules": ["vncviewer"]}], "problemTypes": [{"descriptions": [{"type": "CWE", "cweId": "CWE-193", "lang": "en", "description": "Off-by-one Error"}]}, {"descriptions": [{"type": "CWE", "cweId": "CWE-787", "lang": "en", "description": "Out-of-bounds Write"}]}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH"}}], "references": [{"url": "https://uvnc.com/", "name": "UltraVNC project page", "tags": ["vendor-advisory"]}, {"url": "https://github.com/ultravnc/UltraVNC", "name": "UltraVNC source repository", "tags": ["product"]}, {"url": "https://www.securin.io/zero-days/cve-2026-7831-off-by-one-stack-overflow-viewer-namelength-ultravnc"}], "timeline": [{"time": "2026-06-02T00:00:00.000Z", "lang": "en", "value": "Vulnerability discovered during security audit"}, {"time": "2026-06-17T00:00:00.000Z", "lang": "en", "value": "Reported to vendor (coordinated disclosure)"}, {"time": "2026-09-15T00:00:00.000Z", "lang": "en", "value": "Planned public disclosure (90-day window)"}], "credits": [{"lang": "en", "value": "Arjun Basnet, Securin (arjun.basnet@securin.io)", "type": "finder"}], "source": {"discovery": "EXTERNAL", "advisory": "Securin Security Advisory \u2014 FINDING-011"}, "providerMetadata": {"orgId": "33c584b5-0579-4c06-b2a0-8d8329fcab9c", "shortName": "securin", "dateUpdated": "2026-07-09T04:35:54.891Z"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-07-01T13:12:22.055256Z", "id": "CVE-2026-7831", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-07-01T13:12:46.218Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-7831", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-07-01T13:12:22.055256Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-07-01T13:12:42.509Z"}}], "cna": {"title": "UltraVNC viewer off-by-one stack overflow in ServerInit desktop name parsing", "source": {"advisory": "Securin Security Advisory \u2014 FINDING-011", "discovery": "EXTERNAL"}, "credits": [{"lang": "en", "type": "finder", "value": "Arjun Basnet, Securin (arjun.basnet@securin.io)"}], "metrics": [{"format": "CVSS", "cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 7.5, "attackVector": "NETWORK", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H", "integrityImpact": "LOW", "userInteraction": "REQUIRED", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "LOW"}, "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "affected": [{"vendor": "uvnc", "modules": ["vncviewer"], "product": "UltraVNC", "versions": [{"status": "affected", "version": "0", "versionType": "custom", "lessThanOrEqual": "1.8.2.2"}], "defaultStatus": "unaffected"}], "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)"}], "references": [{"url": "https://uvnc.com/", "name": "UltraVNC project page", "tags": ["vendor-advisory"]}, {"url": "https://github.com/ultravnc/UltraVNC", "name": "UltraVNC source repository", "tags": ["product"]}, {"url": "https://www.securin.io/zero-days/cve-2026-7831-off-by-one-stack-overflow-viewer-namelength-ultravnc"}], "descriptions": [{"lang": "en", "value": "UltraVNC viewer through 1.8.2.2 contains an off-by-one stack buffer overflow in the RFB ServerInit message handler. In vncviewer/ClientConnection.cpp, when the server-supplied nameLength equals exactly 2024 the code declares a 2024-byte stack buffer _dn[2024] and calls ReadString(_dn, 2024). ReadString writes the NUL terminator at buf[length], i.e., _dn[2024], one byte past the end of the stack buffer. A malicious VNC server can trigger this condition by advertising a desktop name of length 2024 in its ServerInit message. On release builds without stack canaries the single-byte NUL overwrite adjacent stack data. On builds with /GS stack protection the canary is corrupted and the process terminates, resulting in denial of service. User interaction (connecting the viewer to the malicious server) is required."}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-193", "description": "Off-by-one Error"}]}, {"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-787", "description": "Out-of-bounds Write"}]}], "providerMetadata": {"orgId": "33c584b5-0579-4c06-b2a0-8d8329fcab9c", "shortName": "securin", "dateUpdated": "2026-07-09T04:35:54.891Z"}}}, "cveMetadata": {"cveId": "CVE-2026-7831", "state": "PUBLISHED", "dateUpdated": "2026-07-09T04:35:54.891Z", "dateReserved": "2026-05-05T04:03:22.622Z", "assignerOrgId": "33c584b5-0579-4c06-b2a0-8d8329fcab9c", "datePublished": "2026-07-01T03:33:25.314Z", "assignerShortName": "securin"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "modules": ["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 viewer through 1.8.2.2 contains an off-by-one stack buffer overflow in the RFB ServerInit message handler. In vncviewer/ClientConnection.cpp, when the server-supplied nameLength equals exactly 2024 the code declares a 2024-byte stack buffer _dn[2024] and calls ReadString(_dn, 2024). ReadString writes the NUL terminator at buf[length], i.e., _dn[2024], one byte past the end of the stack buffer. A malicious VNC server can trigger this condition by advertising a desktop name of length 2024 in its ServerInit message. On release builds without stack canaries the single-byte NUL overwrite adjacent stack data. On builds with /GS stack protection the canary is corrupted and the process terminates, resulting in denial of service. User interaction (connecting the viewer to the malicious server) is required."}, {"lang": "es", "value": "El visor de UltraVNC hasta la versi\u00f3n 1.8.2.2 contiene un desbordamiento de b\u00fafer de pila por un byte (off-by-one) en el gestor de mensajes RFB ServerInit. En vncviewer/ClientConnection.cpp, cuando la longitud del nombre (nameLength) proporcionada por el servidor es exactamente 2024, el c\u00f3digo declara un b\u00fafer de pila de 2024 bytes _dn[2024] y llama a ReadString(_dn, 2024). ReadString escribe el terminador NUL en buf[length], es decir, _dn[2024], un byte m\u00e1s all\u00e1 del final del b\u00fafer de pila. Un servidor VNC malicioso puede desencadenar esta condici\u00f3n al anunciar un nombre de escritorio de longitud 2024 en su mensaje ServerInit. En compilaciones de lanzamiento sin canarios de pila, el NUL de un solo byte sobrescribe datos de pila adyacentes. En compilaciones con protecci\u00f3n de pila /GS, el canario se corrompe y el proceso termina, lo que resulta en una denegaci\u00f3n de servicio. Se requiere interacci\u00f3n del usuario (conectando el visor al servidor malicioso)."}], "id": "CVE-2026-7831", "lastModified": "2026-10-25T17:10:00.197", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.6, "baseSeverity": "HIGH", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 4.7, "source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-7831", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-07-01T13:12:22.055256Z", "version": "2.0.3"}}]}, "published": "2026-07-01T05:16:24.380", "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-2026-7831-off-by-one-stack-overflow-viewer-namelength-ultravnc"}], "sourceIdentifier": "33c584b5-0579-4c06-b2a0-8d8329fcab9c", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-193"}, {"lang": "en", "value": "CWE-787"}], "source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "[0,1.8.2.2]"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "UltraVNC", "source": "cna", "vendor": "uvnc"}, "product": "ultravnc", "vendor": "uvnc"}], "created": "2026-07-01T09:00:14.844033+00:00", "updated": "2026-07-01T15:15:04.136326+00:00", "vendors": ["uvnc", "uvnc$PRODUCT$ultravnc"]}