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CVE-2026-59679 Details

Description

fs_read_glyphs() in the libXfont2 font-server client (src/fc/fserve.c) indexes the per-character encoding[] array using num_chars from the FS_QueryXBitmaps16 reply, but that array was allocated with a size derived from num_extents in the separate FS_QueryXExtents16 reply. The two CARD32 fields are never cross-checked. A malicious or compromised font server can send a small num_extents (e.g. 1) in the extents reply, then a large num_chars (e.g. 100000) in the bitmaps reply. This causes attacker-controlled out-of-bounds heap read and writes.

Metrics

CVSS 3.x Severity and Vector Strings:

CNA: [email protected]CVSS-B:9 CRITICALVector:CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://bugzilla.suse.com/show_bug.cgi?id=CVE-2026-59679	[email protected]

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-787	Out-of-bounds Write	CISA-ADP

Affected Products

No affected product data is available for this CVE.

Change History

2 change records found show changes

Date	Action	Recorded By
Sep 10, 2026	CVE Modified	CISA-ADP
Sep 10, 2026	New CVE Received	[email protected]