CVE-2026-50538

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Source
https://cve.org/CVERecord?id=CVE-2026-50538
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-50538.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-50538
Aliases
  • GHSA-v9pm-47h4-jcq8
Downstream
DEBIAN (1)
MGASA (1)
OESA (4)
openSUSE (2)
SUSE (4)
UBUNTU (1)
Related
openSUSE (2)
SUSE (4)
Published
2026-08-21T21:03:58Z
Modified
2026-10-28T11:16:37Z
Severity
  • 8.8 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H CVSS Calculator
Summary
libvncclient Tight decoder has an attacker-controlled heap out-of-bounds write
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.

Database specific 
{
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
        "CWE-122",
        "CWE-787"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/50xxx/CVE-2026-50538.json"
}
References

Affected packages

Git / github.com/libvnc/libvncserver

Affected ranges

Type
GIT
Repo
https://github.com/libvnc/libvncserver
Events
Introduced
0a70095271d845d16a3ed17354841b01f33963ad
Fixed
540332be3e0acc566fa64da6f1b4680c72c724dd
Database specific
Show details 
{
    "extracted_events": [
        {
            "range": [
                {
                    "introduced": "0.9.12"
                },
                {
                    "last_affected": "0.9.15"
                }
            ],
            "source": "AFFECTED_FIELD",
            "strategy": "StringRangeExpression"
        },
        {
            "range": [
                {
                    "fixed": "540332be3e0acc566fa64da6f1b4680c72c724dd"
                }
            ],
            "source": "REFERENCES_COMMIT"
        }
    ]
}

Affected versions

LibVNCServer-0.*
LibVNCServer-0.9.12
LibVNCServer-0.9.13
LibVNCServer-0.9.14
LibVNCServer-0.9.15

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-50538.json"
vanir_signatures 
[
    {
        "deprecated": false,
        "digest": {
            "function_hash": "164589345870135953612303181283983175944",
            "length": 5063
        },
        "id": "CVE-2026-50538-086a573e",
        "signature_type": "Function",
        "signature_version": "v1",
        "source": "https://github.com/libvnc/libvncserver/commit/540332be3e0acc566fa64da6f1b4680c72c724dd",
        "target": {
            "file": "src/libvncclient/tight.c",
            "function": "HandleTightBPP"
        }
    },
    {
        "deprecated": false,
        "digest": {
            "line_hashes": [
                "214389785877508549493957760394478125992",
                "223103638384069193475657957569529834563",
                "36118045756624052381473943598137507551"
            ],
            "threshold": 0.9
        },
        "id": "CVE-2026-50538-fca2985b",
        "signature_type": "Line",
        "signature_version": "v1",
        "source": "https://github.com/libvnc/libvncserver/commit/540332be3e0acc566fa64da6f1b4680c72c724dd",
        "target": {
            "file": "src/libvncclient/tight.c"
        }
    }
]
vanir_signatures_modified 
"2026-10-28T11:16:37Z"