CVE-2026-59679
criticalpriority · track · 0EPSS 0.003 · 17 %ileDEEPSS · scored 2026-10-27
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.
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · high–critical · 7.2–9.2
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
The CWE weakness classes this flaw belongs to.
affected products (7)
Products and version ranges known to be affected.
advisories (1)
Vendor and ecosystem advisories describing this.
- WID-SEC-W-2026-2658X.Org X11 (libXfont2): Mehrere Schwachstellen ermöglichen Privilegieneskalation und Denial of ServiceDeutsch2026-08-04csaf · cert_bundDE
Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in X.Org X11 ausnutzen, um seine Privilegien zu erhöhen, und um einen Denial of Service Angriff durchzuführen.
sources
Which sources assert this record, and when.
references (1) nvd
External citations — patches, advisories, analysis.
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