CVE-2026-34001

X server crash via freed XSYNC triggers

Published Apr 23, 2026 · Updated Apr 23, 2026

Use-after-free in the XSYNC fence logic in Red Hat Enterprise Linux allows local users with X11 server access to crash the server. The miSyncTriggerFence() loop calls TriggerFence(), which can invoke SyncAwaitTriggerFired() to free the entire await resource while later trigger-list entries remain queued for processing. Access to the X11 server is required; exploitation needs no user interaction and causes a crash, with memory corruption possible in some configurations.

CVSS severity7.8
High
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in the XSYNC fence logic in Red Hat Enterprise Linux allows local users with X11 server access to crash the server. The miSyncTriggerFence() loop calls TriggerFence(), which can invoke SyncAwaitTriggerFired() to free the entire await resource while later trigger-list entries remain queued for processing. Access to the X11 server is required; exploitation needs no user interaction and causes a crash, with memory corruption possible in some configurations.

The record

CVE
CVE-2026-34001
Published
Apr 23, 2026
Updated
Apr 23, 2026
Vendor
389 Directory Server
Product
Red Hat Enterprise Linux 6
Classifications
CWE-825, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 23, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 23, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

389 Directory Server · Red Hat Enterprise Linux 6Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 10Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 7Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 9Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8Affected versions are unavailable in this record.

Published CVSS scores

7.8Red Hat, Inc.CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8Red Hat Security DataCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-825Expired Pointer Dereference
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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