{"api_version":"1","generated_at":"2026-07-03T23:46:02+00:00","cve":"CVE-2026-7831","urls":{"html":"https://cve.report/CVE-2026-7831","api":"https://cve.report/api/cve/CVE-2026-7831.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-7831","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-7831"},"summary":{"title":"UltraVNC viewer off-by-one stack overflow in ServerInit desktop name parsing","description":"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.","state":"PUBLISHED","assigner":"securin","published_at":"2026-07-01 05:16:24","updated_at":"2026-07-02 15:22:26"},"problem_types":["CWE-193","CWE-787","CWE-193 Off-by-one Error","CWE-787 Out-of-bounds Write"],"metrics":[{"version":"3.1","source":"33c584b5-0579-4c06-b2a0-8d8329fcab9c","type":"Secondary","score":"7.6","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H","baseScore":7.6,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"UNCHANGED","confidentialityImpact":"LOW","integrityImpact":"LOW","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"CVSS","score":"7.5","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H","data":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7.5,"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"}}],"references":[{"url":"https://uvnc.com/","name":"https://uvnc.com/","refsource":"33c584b5-0579-4c06-b2a0-8d8329fcab9c","tags":["Product","Release Notes"],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/ultravnc/UltraVNC","name":"https://github.com/ultravnc/UltraVNC","refsource":"33c584b5-0579-4c06-b2a0-8d8329fcab9c","tags":["Product"],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-7831","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-7831","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"uvnc","product":"UltraVNC","version":"affected 1.8.2.2 custom","platforms":[]}],"timeline":[{"source":"CNA","time":"2026-06-02T00:00:00.000Z","lang":"en","value":"Vulnerability discovered during security audit"},{"source":"CNA","time":"2026-06-17T00:00:00.000Z","lang":"en","value":"Reported to vendor (coordinated disclosure)"},{"source":"CNA","time":"2026-09-15T00:00:00.000Z","lang":"en","value":"Planned public disclosure (90-day window)"}],"solutions":[],"workarounds":[],"exploits":[],"credits":[{"source":"CNA","value":"Arjun Basnet, Securin (arjun.basnet@securin.io)","lang":"en"}],"nvd_cpes":[{"cve_year":"2026","cve_id":"7831","vulnerable":"1","versionEndIncluding":"1.8.2.2","cpe1":"cpe","cpe2":"2.3","cpe3":"a","cpe4":"uvnc","cpe5":"ultravnc","cpe6":"*","cpe7":"*","cpe8":"*","cpe9":"*","cpe10":"*","cpe11":"*","cpe12":"*","cpe13":"*"}],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"7831","cve":"CVE-2026-7831","epss":"0.004160000","percentile":"0.334490000","score_date":"2026-07-02","updated_at":"2026-07-03 00:06:10"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"adp":[{"metrics":[{"other":{"content":{"id":"CVE-2026-7831","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","timestamp":"2026-07-01T13:12:22.055256Z","version":"2.0.3"},"type":"ssvc"}}],"providerMetadata":{"dateUpdated":"2026-07-01T13:12:46.218Z","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP"},"title":"CISA ADP Vulnrichment"}],"cna":{"affected":[{"defaultStatus":"unaffected","modules":["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 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."}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7.5,"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"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-193","description":"Off-by-one Error","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-787","description":"Out-of-bounds Write","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-07-01T03:33:25.314Z","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 — FINDING-011","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 viewer off-by-one stack overflow in ServerInit desktop name parsing"}},"cveMetadata":{"assignerOrgId":"33c584b5-0579-4c06-b2a0-8d8329fcab9c","assignerShortName":"securin","cveId":"CVE-2026-7831","datePublished":"2026-07-01T03:33:25.314Z","dateReserved":"2026-05-05T04:03:22.622Z","dateUpdated":"2026-07-01T13:12:46.218Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-07-01 05:16:24","lastModifiedDate":"2026-07-02 15:22:26","problem_types":["CWE-193","CWE-787","CWE-193 Off-by-one Error","CWE-787 Out-of-bounds Write"],"metrics":{"cvssMetricV31":[{"source":"33c584b5-0579-4c06-b2a0-8d8329fcab9c","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H","baseScore":7.6,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"UNCHANGED","confidentialityImpact":"LOW","integrityImpact":"LOW","availabilityImpact":"HIGH"},"exploitabilityScore":2.8,"impactScore":4.7}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-07-01T13:12:22.055256Z","id":"CVE-2026-7831","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:uvnc:ultravnc:*:*:*:*:*:*:*:*","versionEndIncluding":"1.8.2.2","matchCriteriaId":"593F7EC1-0922-4652-817A-7D57A0F1210D"}]}]}]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"7831","Ordinal":"1","Title":"UltraVNC viewer off-by-one stack overflow in ServerInit desktop ","CVE":"CVE-2026-7831","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"7831","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"UltraVNC viewer off-by-one stack overflow in ServerInit desktop "}]}}}