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Description

A flaw was found in the X.Org X server. This integer underflow vulnerability, specifically in the XKB compatibility map handling, allows an attacker with local or remote X11 server access to trigger a buffer read overrun. This can lead to memory-safety violations and potentially a denial of service (DoS) or other severe impacts.

PUBLISHED Reserved 2026-03-25 | Published 2026-04-23 | Updated 2026-04-24 | Assigner redhat




HIGH: 7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Problem types

Integer Underflow (Wrap or Wraparound)

Product status

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affected

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affected

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unknown

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affected

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affected

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affected

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affected

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affected

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affected

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affected

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affected

Timeline

2026-03-25:Reported to Red Hat.
2026-04-23:Made public.

Credits

Red Hat would like to thank Jan-Niklas Sohn (TrendAI Zero Day Initiative) for reporting this issue.

References

access.redhat.com/security/cve/CVE-2026-33999 vdb-entry

bugzilla.redhat.com/show_bug.cgi?id=2451106 (RHBZ#2451106) issue-tracking

cve.org (CVE-2026-33999)

nvd.nist.gov (CVE-2026-33999)

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