CVE catalog

CVE-2026-59679

libxfont: CVE-2026-59679

Severity: Critical · CVSS 9.2CVSS: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
Published: Aug 4, 2026, 10:00:00 PM UTC
Source: [NVD] · [CVE record]
EPSS: 0.26% · Oct 22, 2026

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.

Vulnerable and fixed packages

Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.

Distribution	Package	Release	Version	Status
Debian	libxfont	sid	`1:2.0.9-1`	fixed
Debian	libxfont	forky	`1:2.0.9-1`	fixed
Debian	libxfont	trixie	`1:2.0.6-1+deb13u1`	vulnerable
Debian	libxfont	trixie-security	`1:2.0.6-1+deb13u1`	vulnerable
Debian	libxfont	bookworm	`1:2.0.6-1`	vulnerable
Debian	libxfont	bookworm-security	`1:2.0.6-1+deb12u1`	vulnerable
Ubuntu	libxfont2	16.04	`1:2.0.1-3~ubuntu16.04.1`	vulnerable
Ubuntu	libxfont2	16.04	`1:2.0.1-3~ubuntu16.04.2`	vulnerable
Ubuntu	libxfont2	16.04	`1:2.0.1-3~ubuntu16.04.3`	vulnerable

Fixed-version evidence

Distribution	Package	Type	Release	Fixed version	Urgency	Origin	Bugs
Debian	libxfont	source	sid	`1:2.0.9-1`	unimportant	Not reported	Not reported
Debian	libxfont	source	forky	`1:2.0.9-1`	unimportant	Not reported	Not reported
Debian	libxfont	source	trixie	`(unfixed)`	unimportant	Not reported	Not reported
Debian	libxfont	source	bookworm	`(unfixed)`	unimportant	Not reported	Not reported

OpenFactory catalog packages

[Debian 12 (Bookworm)]

[libxfont2]Affected
Source package: [libxfont]
Details (4)
- 1:2.0.6-1 · amd64 · bookworm
  Affected
  dsa · libxfont · debian · bookworm; dsa · libxfont · debian · 12
- 1:2.0.6-1 · arm64 · bookworm
  Affected
  dsa · libxfont · debian · bookworm; dsa · libxfont · debian · 12
- 1:2.0.6-1+deb12u1 · amd64 · bookworm-security
  Affected
  dsa · libxfont · debian · bookworm; dsa · libxfont · debian · 12
- 1:2.0.6-1+deb12u1 · arm64 · bookworm-security
  Affected
  dsa · libxfont · debian · bookworm; dsa · libxfont · debian · 12
[libxfont-dev]Affected
Source package: [libxfont]
Details (4)
- 1:2.0.6-1 · amd64 · bookworm
  Affected
  dsa · libxfont · debian · bookworm; dsa · libxfont · debian · 12
- 1:2.0.6-1 · arm64 · bookworm
  Affected
  dsa · libxfont · debian · bookworm; dsa · libxfont · debian · 12
- 1:2.0.6-1+deb12u1 · amd64 · bookworm-security
  Affected
  dsa · libxfont · debian · bookworm; dsa · libxfont · debian · 12
- 1:2.0.6-1+deb12u1 · arm64 · bookworm-security
  Affected
  dsa · libxfont · debian · bookworm; dsa · libxfont · debian · 12

[Debian 13 (Trixie)]

[libxfont2]Affected
Source package: [libxfont]
Details (4)
- 1:2.0.6-1+b3 · amd64 · trixie
  Affected
  dsa · libxfont · debian · 13
- 1:2.0.6-1+b3 · arm64 · trixie
  Affected
  dsa · libxfont · debian · 13
- 1:2.0.6-1+deb13u1 · amd64 · trixie-security
  Affected
  dsa · libxfont · debian · 13
- 1:2.0.6-1+deb13u1 · arm64 · trixie-security
  Affected
  dsa · libxfont · debian · 13
[libxfont-dev]Affected
Source package: [libxfont]
Details (4)
- 1:2.0.6-1+b3 · amd64 · trixie
  Affected
  dsa · libxfont · debian · 13
- 1:2.0.6-1+b3 · arm64 · trixie
  Affected
  dsa · libxfont · debian · 13
- 1:2.0.6-1+deb13u1 · amd64 · trixie-security
  Affected
  dsa · libxfont · debian · 13
- 1:2.0.6-1+deb13u1 · arm64 · trixie-security
  Affected
  dsa · libxfont · debian · 13

Observed: Oct 24, 2026, 4:27:23 AM UTC

References

[CERT-Bund public advisories] · [Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX]