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Fencer Vulns
critical 9.0

CVE-2026-59679 json

fs_read_glyphs() heap OOB read/write via encoding array index mismatch in libXfont2

published 2026-09-10 1 mo ago modified 2026-09-10 59 d ago also EUVD-2026-75300

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 17%
public exploits
0
none known

Summary

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.

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-2026-59679

  • 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-101730

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-2026-59679 updated cvss 7.5

libxfont2: Font Server Client encoding[] Out-Of-Bounds Read/Write

  • 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 17% 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 9.2 CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CNA 4.0 9.2 CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/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

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.