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CVE-2026-59679— fs_read_glyphs() heap OOB read/write via encoding array index mismatch in libXfont2

Quick assessment

Affected
SUSE Container suse/kiosk/tigervnc-x11vnc:1.14-63.8
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

函数（位于 libXfont2 字体服务器客户端 中）使用来自 响应中的 作为索引来访问按字符分配的 数组，但该数组的大小是根据另一个独立响应 中的 分配的。这两个 字段之间从未进行交叉验证。 恶意或被入侵的字体服务器可以在 extents 响应中发送一个很小的 （例如 1），然后在 bitmaps 响应中发送一个很大的 （例如 100000）。这会导致攻击者可控的越界堆读取和写入。

CVSS 9.0 · Critical

Possible ATT&CK Techniques 1 AI

T1059 · Command and Scripting Interpreter
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I. Basic Information for CVE-2026-59679

Vulnerability Information
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Vulnerability Title
fs_read_glyphs() heap OOB read/write via encoding array index mismatch in libXfont2
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
SUSE Container suse/kiosk/tigervnc-x11vnc:1.14-63.8 ? ~ 2.0.3-150000.3.6.1 -
SUSE Container suse/kiosk/xorg:21.1-83.7 ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP-Azure ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP-Azure-3P ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP-BYOS ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP-BYOS-Azure ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP-BYOS-EC2 ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP-BYOS-GCE ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP-EC2 ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP-GCE ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP-Hardened ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP-Hardened-Azure ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP-Hardened-BYOS ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP-Hardened-BYOS-Azure ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP-Hardened-BYOS-EC2 ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP-Hardened-BYOS-GCE ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP-Hardened-EC2 ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAP-Hardened-GCE ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAPCAL ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAPCAL-Azure ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAPCAL-EC2 ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP6-SAPCAL-GCE ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP7-SAP-Azure ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP7-SAP-Azure-3P ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP7-SAP-BYOS-Azure ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP7-SAP-BYOS-EC2 ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP7-SAP-BYOS-GCE ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP7-SAP-EC2 ? ~ 2.0.3-150000.3.6.1 -
SUSE Image SLES15-SP7-SAP-GCE ? ~ 2.0.3-150000.3.6.1 -

II. Public POCs for CVE-2026-59679

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III. Intelligence Information for CVE-2026-59679

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Other References for CVE-2026-59679 (1)

IV. Related Vulnerabilities

Same product: Container suse/kiosk/tigervnc-x11vnc:1.14-63.8
Same vendor: SUSE

V. Comments for CVE-2026-59679

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