{"id":"DEBIAN-CVE-2026-50538","details":"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 is 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.","modified":"2026-09-01T16:06:48.524789954Z","published":"2026-08-21T21:16:59.807Z","upstream":["CVE-2026-50538"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-50538"}],"affected":[{"package":{"name":"libvncserver","ecosystem":"Debian:12","purl":"pkg:deb/debian/libvncserver?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.9.14+dfsg-1+deb12u2"}]}],"versions":["0.9.14+dfsg-1","0.9.14+dfsg-1+deb12u1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-50538.json"}},{"package":{"name":"libvncserver","ecosystem":"Debian:13","purl":"pkg:deb/debian/libvncserver?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.9.15+dfsg-1+deb13u2"}]}],"versions":["0.9.15+dfsg-1","0.9.15+dfsg-1+deb13u1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-50538.json"}},{"package":{"name":"libvncserver","ecosystem":"Debian:14","purl":"pkg:deb/debian/libvncserver?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.9.15+dfsg-6"}]}],"versions":["0.9.15+dfsg-1","0.9.15+dfsg-2","0.9.15+dfsg-3","0.9.15+dfsg-4","0.9.15+dfsg-5"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-50538.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"}]}