CVE-2026-50538

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{"affected": [{"affectedData": [{"product": "libvncserver", "vendor": "LibVNC", "versions": [{"status": "affected", "version": ">= 0.9.12, <= 0.9.15"}]}], "source": "security-advisories@github.com"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "LibVNCClient is a library for easy implementation of a VNC client. In versions 0.9.12 through 0.9.15, a malicious (or man-in-the-middle) VNC server can force a connecting `libvncclient` to write attacker-controlled data past the end of its framebuffer. This is an out-of-bounds heap write with attacker-controlled length, contents, and offset. It needs no authentication (the attacker\nis the server), works in a default build with default settings, and fires from a single `FramebufferUpdate` the moment the victim connects. It crashes any client unconditionally (denial of service); we also demonstrated it overwriting an application callback pointer and redirecting execution to attacker-chosen code (code execution) under the default configuration. Commit 540332be3e0acc566fa64da6f1b4680c72c724dd patches the issue."}, {"lang": "es", "value": "LibVNCClient es una biblioteca para la f\u00e1cil implementaci\u00f3n de un cliente VNC. En las versiones 0.9.12 a la 0.9.15, un servidor VNC malicioso (o man-in-the-middle) puede forzar a un 'libvncclient' que se conecta a escribir datos controlados por el atacante m\u00e1s all\u00e1 del final de su framebuffer. Esto es una escritura de heap fuera de l\u00edmites con longitud, contenido y desplazamiento controlados por el atacante. No necesita autenticaci\u00f3n (el atacante es el servidor), funciona en una compilaci\u00f3n predeterminada con configuraciones predeterminadas, y se activa desde una \u00fanica 'FramebufferUpdate' en el momento en que la v\u00edctima se conecta. Bloquea cualquier cliente incondicionalmente (denegaci\u00f3n de servicio); tambi\u00e9n demostramos que sobrescribe un puntero de callback de aplicaci\u00f3n y redirige la ejecuci\u00f3n a c\u00f3digo elegido por el atacante (ejecuci\u00f3n de c\u00f3digo) bajo la configuraci\u00f3n predeterminada. El commit 540332be3e0acc566fa64da6f1b4680c72c724dd corrige el problema."}], "id": "CVE-2026-50538", "lastModified": "2026-10-12T16:10:00.220", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 8.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 5.9, "source": "security-advisories@github.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-50538", "options": [{"exploitation": "poc"}, {"automatable": "no"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-08-24T19:39:31.246844Z", "version": "2.0.3"}}]}, "published": "2026-08-21T21:16:59.807", "references": [{"source": "security-advisories@github.com", "url": "https://github.com/LibVNC/libvncserver/commit/540332be3e0acc566fa64da6f1b4680c72c724dd"}, {"source": "security-advisories@github.com", "url": "https://github.com/LibVNC/libvncserver/security/advisories/GHSA-v9pm-47h4-jcq8"}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "url": "https://github.com/LibVNC/libvncserver/security/advisories/GHSA-v9pm-47h4-jcq8"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Deferred", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-122"}, {"lang": "en", "value": "CWE-787"}], "source": "security-advisories@github.com", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0.9.12,0.9.15]"}}], "enrichment": {"confidence": 86.0, "confidence_source": "matching", "scores": [{"score": 86.0, "source": "matching"}]}, "original": {"product": "libvncserver", "source": "cna", "vendor": "LibVNC"}, "product": "libvncserver", "vendor": "libvncserver"}], "created": "2026-08-21T22:45:04.683181+00:00", "updated": "2026-08-24T21:00:12.178954+00:00", "vendors": ["libvncserver", "libvncserver$PRODUCT$libvncserver"]}