{"id":"DEBIAN-CVE-2026-59679","details":"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.","modified":"2026-09-11T06:00:09.226030256Z","published":"2026-09-10T09:17:02.883Z","upstream":["CVE-2026-59679"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-59679"}],"affected":[{"package":{"name":"libxfont","ecosystem":"Debian:12","purl":"pkg:deb/debian/libxfont?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:2.0.6-1","1:2.0.6-1+deb12u1","1:2.0.6-1+hurd.1","1:2.0.6-2","1:2.0.8-1","1:2.0.9-1"],"ecosystem_specific":{"urgency":"unimportant"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-59679.json"}},{"package":{"name":"libxfont","ecosystem":"Debian:13","purl":"pkg:deb/debian/libxfont?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:2.0.6-1","1:2.0.6-1+deb13u1","1:2.0.6-1+hurd.1","1:2.0.6-2","1:2.0.8-1","1:2.0.9-1"],"ecosystem_specific":{"urgency":"unimportant"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-59679.json"}},{"package":{"name":"libxfont","ecosystem":"Debian:14","purl":"pkg:deb/debian/libxfont?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:2.0.9-1"}]}],"versions":["1:2.0.6-1","1:2.0.6-1+hurd.1","1:2.0.6-2","1:2.0.8-1"],"ecosystem_specific":{"urgency":"unimportant"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-59679.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}]}