{"id":"CVE-2026-50538","aliases":["DEBIAN-CVE-2026-50538","EUVD-2026-64167","GHSA-v9pm-47h4-jcq8","MGASA-2026-0315","OESA-2026-3318","OESA-2026-3319","OESA-2026-3320","OESA-2026-3489","SUSE-SU-2026:23601-1","SUSE-SU-2026:3803-1","SUSE-SU-2026:4022-1","SUSE-SU-2026:4024-1","UBUNTU-CVE-2026-50538","USN-8494-1","openSUSE-SU-2026:11601-1","openSUSE-SU-2026:21735-1"],"status":"published","title":"libvncclient Tight decoder has an attacker-controlled heap out-of-bounds write","description":"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.","severity":{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00404,"percentile":0.35075,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-122","CWE-787"],"published":"2026-06-15T00:00:00Z","modified":"2026-10-28T11:16:37Z","fixes":[{"ecosystem":"Debian:12","package":"libvncserver","fixed_in":["0.9.14+dfsg-1+deb12u2"],"sources":["osv"]},{"ecosystem":"Debian:13","package":"libvncserver","fixed_in":["0.9.15+dfsg-1+deb13u2"],"sources":["osv"]},{"ecosystem":"Debian:14","package":"libvncserver","fixed_in":["0.9.15+dfsg-6"],"sources":["osv"]},{"ecosystem":"openEuler:24.03-LTS-SP1","package":"libvncserver","fixed_in":["0.9.13-6.oe2403sp1"],"sources":["osv"]},{"ecosystem":"openEuler:24.03-LTS-SP3","package":"libvncserver","fixed_in":["0.9.13-6.oe2403sp3"],"sources":["osv"]},{"ecosystem":"openEuler:22.03-LTS-SP4","package":"libvncserver","fixed_in":["0.9.13-6.oe2203sp4"],"sources":["osv"]},{"ecosystem":"openEuler:24.03-LTS-SP4","package":"libvncserver","fixed_in":["0.9.13-6.oe2403sp4"],"sources":["osv"]},{"ecosystem":"SUSE:Linux 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Tight decoder has an attacker-controlled heap out-of-bounds write","description":"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.","status":"published","published":"2026-08-21T21:03:58.147Z","modified":"2026-08-24T19:39:57.811Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-122","CWE-787"],"updated_at":"2026-11-02T14:20:08.734143Z"}],"euvd":[{"id":"EUVD-2026-64167","description":"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.","status":"published","published":"2026-08-21T21:03:58Z","modified":"2026-08-24T19:39:57Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-02T18:01:34.230875Z"}],"nvd":[{"id":"CVE-2026-50538","description":"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.","status":"published","published":"2026-08-21T21:16:59.807Z","modified":"2026-10-12T16:10:00.22Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-122","CWE-787"],"updated_at":"2026-11-02T14:12:40.665005Z"}],"osv":[{"id":"CVE-2026-50538","title":"libvncclient Tight decoder has an attacker-controlled heap out-of-bounds write","description":"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.","status":"published","published":"2026-08-21T21:03:58.147Z","modified":"2026-10-28T11:16:37.21535018Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-122","CWE-787"],"updated_at":"2026-11-02T15:45:07.431113Z"},{"id":"DEBIAN-CVE-2026-50538","description":"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.","status":"published","published":"2026-08-21T21:16:59.807Z","modified":"2026-10-13T09:47:41.803429028Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-02T15:45:56.877408Z"},{"id":"OESA-2026-3318","title":"libvncserver security update","description":"libvncserver is a set of programs using the RFB (Remote Frame Buffer) protocol. They are designed to \u0026amp;quot;export\u0026amp;quot; a frame buffer via net: you set up a server and can connect to it via VNC viewers. If the server supports WebSockets (which LibVNCServer does), you can also connect using an in-browser VNC viewer like noVNC. It is already in wide use for administration, but it is not that easy to program a server yourself.\r\n\r\nSecurity Fix(es):\n\nAn attacker-controlled heap out-of-bounds write vulnerability exists in the Tight decoder of libvncclient within libvncserver. An attacker can trigger a heap out-of-bounds write via crafted packets, potentially leading to denial of service or remote code execution.(CVE-2026-50538)","status":"published","published":"2026-08-13T13:57:19Z","modified":"2026-08-16T01:45:09.237404755Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-02T15:52:46.823443Z"},{"id":"OESA-2026-3319","title":"libvncserver security update","description":"libvncserver is a set of programs using the RFB (Remote Frame Buffer) protocol. They are designed to \u0026amp;quot;export\u0026amp;quot; a frame buffer via net: you set up a server and can connect to it via VNC viewers. If the server supports WebSockets (which LibVNCServer does), you can also connect using an in-browser VNC viewer like noVNC. It is already in wide use for administration, but it is not that easy to program a server yourself.\r\n\r\nSecurity Fix(es):\n\nAn attacker-controlled heap out-of-bounds write vulnerability exists in the Tight decoder of libvncclient within libvncserver. An attacker can trigger a heap out-of-bounds write via crafted packets, potentially leading to denial of service or remote code execution.(CVE-2026-50538)","status":"published","published":"2026-08-13T13:57:20Z","modified":"2026-08-16T01:45:10.726640233Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-02T15:52:46.823443Z"},{"id":"OESA-2026-3320","title":"libvncserver security update","description":"libvncserver is a set of programs using the RFB (Remote Frame Buffer) protocol. They are designed to \u0026amp;quot;export\u0026amp;quot; a frame buffer via net: you set up a server and can connect to it via VNC viewers. If the server supports WebSockets (which LibVNCServer does), you can also connect using an in-browser VNC viewer like noVNC. It is already in wide use for administration, but it is not that easy to program a server yourself.\r\n\r\nSecurity Fix(es):\n\nAn attacker-controlled heap out-of-bounds write vulnerability exists in the Tight decoder of libvncclient within libvncserver. An attacker can trigger a heap out-of-bounds write via crafted packets, potentially leading to denial of service or remote code execution.(CVE-2026-50538)","status":"published","published":"2026-08-13T13:57:21Z","modified":"2026-08-16T01:45:09.279304574Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-02T15:52:46.823443Z"},{"id":"OESA-2026-3489","title":"libvncserver security update","description":"libvncserver is a set of programs using the RFB (Remote Frame Buffer) protocol. They are designed to \u0026amp;quot;export\u0026amp;quot; a frame buffer via net: you set up a server and can connect to it via VNC viewers. If the server supports WebSockets (which LibVNCServer does), you can also connect using an in-browser VNC viewer like noVNC. It is already in wide use for administration, but it is not that easy to program a server yourself.\r\n\r\nSecurity Fix(es):\n\nAn attacker-controlled heap out-of-bounds write vulnerability exists in the Tight decoder of libvncclient within libvncserver. An attacker can trigger a heap out-of-bounds write via crafted packets, potentially leading to denial of service or remote code execution.(CVE-2026-50538)","status":"published","published":"2026-08-20T10:01:48Z","modified":"2026-08-20T10:15:10.846592494Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-02T15:52:47.217107Z"},{"id":"UBUNTU-CVE-2026-50538","description":"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.","status":"published","published":"2026-06-15T00:00:00Z","modified":"2026-10-17T12:59:00.374285906Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-02T16:56:33.391918Z"},{"id":"MGASA-2026-0315","title":"Updated libvncserver packages fix security vulnerabilities","description":"The updated packages fix security vulnerabilities:\nHeap Out-of-Bounds Read in HandleUltraZipBPP due to unchecked\nsubrectangle count. (CVE-2026-32853)\nNULL pointer dereferences in httpd proxy handlers via malformed\nCONNECT/GET requests. (CVE-2026-32854)\nLibVNCClient Tight Gradient decoding allows malicious server-triggered\nheap/stack OOB writes. (CVE-2026-44988)\nAttacker-controlled heap out-of-bounds write in libvncclient Tight\ndecoder. (CVE-2026-50538)\n","status":"published","published":"2026-08-03T18:47:23Z","modified":"2026-08-03T19:00:05.507881509Z","updated_at":"2026-11-02T15:49:43.795591Z"},{"id":"openSUSE-SU-2026:11601-1","title":"LibVNCServer-devel-0.9.15-4.1 on GA media","description":"These are all security issues fixed in the LibVNCServer-devel-0.9.15-4.1 package on the GA media of openSUSE Tumbleweed.","status":"published","published":"2026-08-26T00:00:00Z","modified":"2026-08-27T11:01:38.288773608Z","updated_at":"2026-11-02T16:58:39.516824Z"},{"id":"openSUSE-SU-2026:21735-1","title":"Security update for LibVNCServer","description":"This update for LibVNCServer fixes the following issue:\n\n- CVE-2026-50538: malicious or MiTM VNC servers can force a connecting `libvncclient` to write attacker-controlled data\n  past the end of a framebuffer, which can lead to a crash or arbitrary code execution (bsc#1276218).\n","status":"published","published":"2026-09-02T09:40:22Z","modified":"2026-09-09T18:23:13.422053511Z","updated_at":"2026-11-02T16:58:42.426393Z"},{"id":"SUSE-SU-2026:23601-1","title":"Security update for LibVNCServer","description":"This update for LibVNCServer fixes the following issue:\n\n- CVE-2026-50538: malicious or MiTM VNC servers can force a connecting `libvncclient` to write attacker-controlled data\n  past the end of a framebuffer, which can lead to a crash or arbitrary code execution (bsc#1276218).\n","status":"published","published":"2026-09-02T09:37:55Z","modified":"2026-09-29T18:23:19.005527662Z","updated_at":"2026-11-02T15:54:03.991985Z"},{"id":"SUSE-SU-2026:3803-1","title":"Security update for LibVNCServer","description":"This update for LibVNCServer fixes the following issue:\n\n- CVE-2026-50538: a malicious (or man-in-the-middle) VNC server can force a connecting `libvncclient` to write attacker-\n  controlled data past the end of its framebuffer (bsc#1276218).\n","status":"published","published":"2026-08-25T18:48:49Z","modified":"2026-08-31T18:23:10.02676211Z","updated_at":"2026-11-02T15:54:05.392906Z"},{"id":"SUSE-SU-2026:4022-1","title":"Security update for LibVNCServer","description":"This update for LibVNCServer fixes the following issue:\n\n- CVE-2026-50538: a malicious (or man-in-the-middle) VNC server can force a connecting `libvncclient` to write attacker-\n  controlled data past the end of its framebuffer (bsc#1276218).\n","status":"published","published":"2026-09-07T07:42:44Z","modified":"2026-09-13T18:23:16.111607689Z","updated_at":"2026-11-02T15:54:05.392906Z"},{"id":"SUSE-SU-2026:4024-1","title":"Security update for LibVNCServer","description":"This update for LibVNCServer fixes the following issue:\n\n- CVE-2026-50538: a malicious (or man-in-the-middle) VNC server can force a connecting `libvncclient` to write attacker-\n  controlled data past the end of its framebuffer (bsc#1276218).\n","status":"published","published":"2026-09-07T07:43:06Z","modified":"2026-09-13T18:23:16.157356767Z","updated_at":"2026-11-02T15:54:05.392906Z"},{"id":"USN-8494-1","title":"libvncserver vulnerability","description":"It was discovered that LibVNCServer incorrectly handled the Tight decoder\nin libvncclient. A remote attacker could use this issue to cause\nLibVNCServer to crash, resulting in a denial of service, or possibly\nexecute arbitrary code.","status":"published","published":"2026-07-02T13:22:47Z","modified":"2026-08-24T10:00:16.883598277Z","updated_at":"2026-11-02T16:58:25.103481Z"}]}}