CVE-2026-59679
fs_read_glyphs() heap OOB read/write via encoding array index mismatch in libXfont2
No known exploitation. EPSS puts it in the 32nd percentile. No fix published yet.
What to do
No fixed build or workaround is published yet. Limit exposure and watch for a patch.
What it is
From the CVE record
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.
In plain language
No plain-language summary for this CVE yet.
Exploitation
Where each signal puts this CVE on the scale from published to confirmed exploited.
- CISA KEV
Not in the catalog. CISA has not confirmed exploitation.
- Public exploits
No public exploit or proof of concept found in the sources we track.
- EPSS
0.4% chance of exploitation activity in the next 30 days, which ranks it in the 32nd percentile of scored CVEs.
Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.
Lifecycle
6 events over 33 days, from the signal feeds we watch.
- Publishedweakness classified, att&ck mapped, record updated, record updated
- OpenVAS check added
Affected products
- Container suse/kiosk/tigervnc-x11vnc:1.14-63.8Operating Systems / linux-distro
- Container suse/kiosk/xorg:21.1-83.7Operating Systems / linux-distro
- Image SLES15-SP6-SAPOperating Systems / linux-distro
- Image SLES15-SP6-SAP-AzureOperating Systems / linux-distro
- Image SLES15-SP6-SAP-Azure-3POperating Systems / linux-distro
- Image SLES15-SP6-SAP-BYOSOperating Systems / linux-distro
- Image SLES15-SP6-SAP-BYOS-AzureOperating Systems / linux-distro
- Image SLES15-SP6-SAP-BYOS-EC2Operating Systems / linux-distro
And 71 more affected products. See all after sign-in
Technical detail
CVSS 3.1 vector
Open in the CVSS calculatorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Scored 9.0 by NVD.
How it is reached
- Attack Vector NetworkExploitable remotely over the network without any special conditions
- Attack Complexity HighRequires specific conditions like a race condition or non-default configuration
- Privileges Required NoneNo authentication required — anyone can exploit this
- User Interaction NoneNo user interaction needed — fully automated exploitation
Scope
- Scope ChangedThe exploit can affect other components (e.g. sandbox escape, host compromise from VM)
Impact if exploited
- Confidentiality HighTotal information disclosure — all data in the component is compromised
- Integrity HighTotal loss of integrity — attacker can modify any data in the component
- Availability HighTotal denial of service — the component is completely unavailable
Weaknesses
ATT&CK techniques
Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.
- Initial AccessT1190Exploit Public-Facing Applicationhigh confidence
- Privilege EscalationT1068Exploitation for Privilege Escalationhigh confidence
Sources
References in the record
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