Buffer overflow in Libxfont2
CVE-2026-59679
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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.0 (Critical). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.003 (16.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 16th percentile — 16.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.003 · change: -0.001
Affected products
- Libxfont2
- SUSE openSUSE Tumbleweed
- SUSE Linux Enterprise Desktop 15 Sp7
- SUSE Linux Enterprise High Performance Computing 15 Sp4-Espos
- SUSE Linux Enterprise High Performance Computing 15 Sp4-Ltss
- SUSE Linux Enterprise High Performance Computing 15 Sp5-Espos
- SUSE Linux Enterprise High Performance Computing 15 Sp5-Ltss
- SUSE Linux Enterprise Module For Basesystem 15 Sp7
- SUSE Linux Enterprise Server 15 Sp4-Ltss
- SUSE Linux Enterprise Server 15 Sp5-Ltss
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-59679?
- CVE-2026-59679 is a critical-severity vulnerability in Libxfont2, classified under Out-of-bounds Write. CVSS score: 9.0/10. Published 2026-09-10.
- How severe is CVE-2026-59679?
- Critical severity. CVSS v3 base score is 9.0 out of 10.