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Fencer Vulns
critical 9.0

CVE-2026-44950 json

fs_read_glyphs() heap buffer overflow via cumulative glyph data overflow in libXfont2

published 2026-09-10 1 mo ago modified 2026-09-10 59 d ago also EUVD-2026-75306

cvss
9.0
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 18%
public exploits
0
none known

Summary

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.

Patch / fix

  • 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
  • libxfont Debian 14 1:2.0.9-1

debian advisories DEBIAN-CVE-2026-44950

  • libXfont2 RHEL 8 2.0.3-2.el8_10.3
  • libXfont2 RHEL 10.2 2.0.6-5.el10_2.3
  • libXfont2 RHEL 9 2.0.3-12.el9_8.3
  • libXfont2 RHEL 7 ELS 2.0.3-3.el7_9
  • libXfont2 enterprise linux eus 10.0 2.0.6-5.el10_0.2
  • libXfont2 RHEL 8.4 EUS_LONG_LIFE, RHEL 8.4 AUS 2.0.3-2.el8_4.2
  • libXfont2 RHEL 8.6 EUS_LONG_LIFE, RHEL 8.6 AUS 2.0.3-2.el8_6.2
  • libXfont2 RHEL 8.8 TUS, RHEL 8.8 E4S 2.0.3-2.el8_8.2

red hat advisories RHSA-2026:62231RHSA-2026:62123RHSA-2026:61995RHSA-2026:61755RHSA-2026:61756RHSA-2026:61390

  • libXfont2 SLES 16.0, SLES for SAP applications 16.0 2.0.7-160000.5.1
  • libXfont2 SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +8 more 2.0.3-150000.3.6.1
  • libXfont2 SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 2.0.3-3.6.1

suse advisories SUSE-SU-2026:23128-1SUSE-SU-2026:23151-1SUSE-SU-2026:3500-1SUSE-SU-2026:3499-1

  • libXfont2 openSUSE Leap 16.0 2.0.7-160000.5.1
  • libXfont2 openSUSE Tumbleweed 2.0.7-3.1

opensuse advisories openSUSE-SU-2026:21539-1openSUSE-SU-2026:11463-1

  • libXfont2 AlmaLinux 8 2.0.3-2.el8_10.3
  • libXfont2 AlmaLinux 9 2.0.3-12.el9_8.3
  • libXfont2 AlmaLinux 10 2.0.6-5.el10_2.3

almalinux advisories ALSA-2026:55446ALSA-2026:55447ALSA-2026:55448

  • libXfont2 Rocky Linux 10 2.0.6-5.el10_2.3
  • libXfont2 Rocky Linux 9 2.0.3-12.el9_8.3
  • libXfont2 Rocky Linux 8 2.0.3-2.el8_10.3

rocky linux advisories RLSA-2026:55448RLSA-2026:55447RLSA-2026:55446

  • libXfont2 Azure Linux 3.0 2.0.9-1

azure linux advisories AZL-101733

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-44950 updated cvss 7.5

libxfont2: libXfont2: Privilege Escalation via Heap Buffer Overflow in Font Server Client

  • Red Hat CodeReady Linux Builder EUS (v.9.6) libXfont2-devel 2.0.3-12.el9_6.3, libXfont2-debuginfo 2.0.3-12.el9_6.3, libXfont2-debugsource 2.0.3-12.el9_6.3
    fixed: vendor fix RHSA-2026:61390
  • Red Hat Enterprise Linux AppStream (v. 8) libXfont2 2.0.3-2.el8_10.3
    fixed: vendor fix RHSA-2026:55446
  • Red Hat Enterprise Linux AppStream (v. 9) libXfont2 2.0.3-12.el9_8.3
    fixed: vendor fix RHSA-2026:55447
  • Red Hat Enterprise Linux AppStream (v. 10) libXfont2 2.0.6-5.el10_2.3
    fixed: vendor fix RHSA-2026:55448
  • Red Hat Enterprise Linux AppStream AUS (v.8.4) libXfont2 2.0.3-2.el8_4.2
    fixed: vendor fix RHSA-2026:61995
  • Red Hat Enterprise Linux AppStream AUS (v.8.6) libXfont2 2.0.3-2.el8_6.2
    fixed: vendor fix RHSA-2026:61755
  • Red Hat Enterprise Linux AppStream E4S (v.8.8) libXfont2 2.0.3-2.el8_8.2
    fixed: vendor fix RHSA-2026:61756
  • Red Hat Enterprise Linux AppStream E4S (v.9.2) libXfont2 2.0.3-12.el9_2.3
    fixed: vendor fix RHSA-2026:59311
show 11 more
  • Red Hat Enterprise Linux AppStream E4S (v.9.4) libXfont2 2.0.3-12.el9_4.3
    fixed: vendor fix RHSA-2026:59312
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) libXfont2 2.0.6-5.el10_0.2
    fixed: vendor fix RHSA-2026:62123
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) libXfont2 2.0.3-12.el9_6.3
    fixed: vendor fix RHSA-2026:61390
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) libXfont2 2.0.3-2.el8_4.2
    fixed: vendor fix RHSA-2026:61995
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) libXfont2 2.0.3-2.el8_6.2
    fixed: vendor fix RHSA-2026:61755
  • Red Hat Enterprise Linux AppStream TUS (v.8.8) libXfont2 2.0.3-2.el8_8.2
    fixed: vendor fix RHSA-2026:61756
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libXfont2-devel 2.0.3-12.el9_8.3, libXfont2-debuginfo 2.0.3-12.el9_8.3, libXfont2-debugsource 2.0.3-12.el9_8.3
    fixed: vendor fix RHSA-2026:55447
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libXfont2-devel 2.0.6-5.el10_2.3, libXfont2-debuginfo 2.0.6-5.el10_2.3, libXfont2-debugsource 2.0.6-5.el10_2.3
    fixed: vendor fix RHSA-2026:55448
  • Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0) libXfont2-devel 2.0.6-5.el10_0.2, libXfont2-debuginfo 2.0.6-5.el10_0.2, libXfont2-debugsource 2.0.6-5.el10_0.2
    fixed: vendor fix RHSA-2026:62123
  • Red Hat Enterprise Linux CRB (v. 8) libXfont2-devel 2.0.3-2.el8_10.3, libXfont2-debuginfo 2.0.3-2.el8_10.3, libXfont2-debugsource 2.0.3-2.el8_10.3
    fixed: vendor fix RHSA-2026:55446
  • Red Hat Enterprise Linux Server (v. 7 ELS) libXfont2 2.0.3-3.el7_9 Red Hat Enterprise Linux Server Optional (v. 7 ELS) libXfont2-devel 2.0.3-3.el7_9, libXfont2-debuginfo 2.0.3-3.el7_9
    fixed: vendor fix RHSA-2026:62231

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
59 d ago

Exploit prediction

0.26% chance of exploitation in the next 30 days, higher than 18% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 9.0 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
CNA 4.0 9.5 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
CNA 4.0 9.5 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • SUSE Container suse/kiosk/tigervnc-x11vnc:1.14-63.8
  • SUSE Container suse/kiosk/xorg:21.1-83.7
  • SUSE Image SLES15-SP6-SAP
  • SUSE Image SLES15-SP6-SAP-Azure
  • SUSE Image SLES15-SP6-SAP-Azure-3P
  • SUSE Image SLES15-SP6-SAP-BYOS
  • SUSE Image SLES15-SP6-SAP-BYOS-Azure
  • SUSE Image SLES15-SP6-SAP-BYOS-EC2
  • SUSE Image SLES15-SP6-SAP-BYOS-GCE
  • SUSE Image SLES15-SP6-SAP-EC2
  • SUSE Image SLES15-SP6-SAP-GCE
  • SUSE Image SLES15-SP6-SAP-Hardened
  • SUSE Image SLES15-SP6-SAP-Hardened-Azure
  • SUSE Image SLES15-SP6-SAP-Hardened-BYOS
  • SUSE Image SLES15-SP6-SAP-Hardened-BYOS-Azure
  • SUSE Image SLES15-SP6-SAP-Hardened-BYOS-EC2
  • SUSE Image SLES15-SP6-SAP-Hardened-BYOS-GCE
  • SUSE Image SLES15-SP6-SAP-Hardened-EC2
  • SUSE Image SLES15-SP6-SAP-Hardened-GCE
  • SUSE Image SLES15-SP6-SAPCAL
  • SUSE Image SLES15-SP6-SAPCAL-Azure
  • SUSE Image SLES15-SP6-SAPCAL-EC2
  • SUSE Image SLES15-SP6-SAPCAL-GCE
  • SUSE Image SLES15-SP7-SAP-Azure
  • SUSE Image SLES15-SP7-SAP-Azure-3P
  • SUSE Image SLES15-SP7-SAP-BYOS-Azure
  • SUSE Image SLES15-SP7-SAP-BYOS-EC2
  • SUSE Image SLES15-SP7-SAP-BYOS-GCE
  • SUSE Image SLES15-SP7-SAP-EC2
  • SUSE Image SLES15-SP7-SAP-GCE
  • SUSE Image SLES15-SP7-SAP-GCE-3P
  • SUSE Image SLES15-SP7-SAP-Hardened-Azure
  • SUSE Image SLES15-SP7-SAP-Hardened-BYOS-Azure
  • SUSE Image SLES15-SP7-SAP-Hardened-BYOS-EC2
  • SUSE Image SLES15-SP7-SAP-Hardened-BYOS-GCE
  • SUSE Image SLES15-SP7-SAP-Hardened-GCE
  • SUSE Image SLES15-SP7-SAPCAL-Azure
  • SUSE Image SLES15-SP7-SAPCAL-EC2
  • SUSE Image SLES15-SP7-SAPCAL-GCE
  • SUSE Image SLES-SAP-Azure
  • SUSE Image SLES-SAP-Azure-3P
  • SUSE Image SLES-SAP-BYOS-Azure
  • SUSE Image SLES-SAP-BYOS-EC2
  • SUSE Image SLES-SAP-BYOS-GCE
  • SUSE Image SLES-SAP-GCE
  • SUSE Image SLES-SAP-GCE-3P
  • SUSE Image SLES-SAPCAL-GCE
  • SUSE Image SLES12-SP5-Azure-SAP-BYOS
  • SUSE Image SLES12-SP5-Azure-SAP-On-Demand
  • SUSE Image SLES12-SP5-EC2-SAP-BYOS

Classification

Weakness
  • CWE-122 Heap-based Buffer Overflow

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.