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CVE-2026-44950— fs_read_glyphs() heap buffer overflow via cumulative glyph data overflow 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.

libXfont2 字体服务器客户端（位于 ）中的 函数将每个字形的位图数据复制到一个单独的缓冲区。现有的检查仅验证源数据片段（位置、长度）是否位于源位图缓冲区内，但没有检查目标写入光标是否已超出目标缓冲区的分配大小。 恶意字体服务器可以发送存在重叠的源偏移量——例如，发送 1000 个字形，每个字形均引用 ，且 。虽然每个独立的源范围都能通过现有的验证，但累积的写入总量为 64000 字节，而目标缓冲区仅有 64 字节。这导致了一个由攻击者控制内容的堆缓冲区溢出。

CVSS 9.0 · Critical

Possible ATT&CK Techniques 1 AI

T1029 · Scheduled Transfer
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I. Basic Information for CVE-2026-44950

Vulnerability Information
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Vulnerability Title
fs_read_glyphs() heap buffer overflow via cumulative glyph data overflow in libXfont2
Source: CVE Program / CVE List V5
Vulnerability Description
fs_read_glyphs() in the libXfont2 font-server client (src/fc/fserve.c) copies each glyph's bitmap into a single buffer. Existing checks validates only that the source slice (position, length) lies within the source bitmap buffer. It does not check whether the running destination cursor has exceeded the allocation. A malicious font server can send overlapping source offsets -- for example 1000 glyphs each referencing {position:0, length:64} with nbytes=64. Each individual source range passes the existing validation, but the cumulative writes total 64000 bytes into a 64-byte destination buffer. This is a heap buffer overflow with attacker-controlled content.
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-2026-44950

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III. Intelligence Information for CVE-2026-44950

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Other References for CVE-2026-44950 (1)

IV. Related Vulnerabilities

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

V. Comments for CVE-2026-44950

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