GHSA-5P7P-JGVJ-4V95

Vulnerability from github – Published: 2026-06-05 12:31 – Updated: 2026-08-05 00:30
VLAI
Details

A use-after-free flaw was found in the X.Org X server and Xwayland in miSyncDestroyFence(). A client that sets up multiple fence triggers can trigger a use-after-free function pointer call. An attacker would connect to the X server to set up a fence and await that fence, then a second X connection destroys the fence, causing the use-after-free. This may be used to crash the server, or for privilege escalation if the X server runs as root.

Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-50257"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-416"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-06-05T12:16:38Z",
    "severity": "HIGH"
  },
  "details": "A use-after-free flaw was found in the X.Org X server and Xwayland in miSyncDestroyFence(). A client that sets up multiple fence triggers can trigger a use-after-free function pointer call. An attacker would connect to the X server to set up a fence and await that fence, then a second X connection destroys the fence, causing the use-after-free. This may be used to crash the server, or for privilege escalation if the X server runs as root.",
  "id": "GHSA-5p7p-jgvj-4v95",
  "modified": "2026-08-05T00:30:33Z",
  "published": "2026-06-05T12:31:46Z",
  "references": [
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      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50257"
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      "type": "CVSS_V3"
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}



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