UBUNTU-CVE-2026-59679

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Source

https://ubuntu.com/security/CVE-2026-59679

Import Source

https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-59679.json

JSON Data

https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-59679

Upstream

CVE-2026-59679

Published

2026-09-10T09:17:00Z

Modified

2026-09-28T17:30:05Z

Severity

9.0 (Critical) CVSS_V3 - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H CVSS Calculator
9.2 (Critical) CVSS_V4 - 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 CVSS Calculator
Ubuntu - medium

Summary

[none]

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.

References

Affected packages

Ubuntu:16.04:LTS / libxfont2

Package

Name: libxfont2
Purl: pkg:deb/ubuntu/libxfont2?arch=source&distro=xenial

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0 Unknown introduced version / All previous versions are affected

Affected versions

1:2.*

1:2.0.1-3~ubuntu16.04.1

1:2.0.1-3~ubuntu16.04.2

1:2.0.1-3~ubuntu16.04.3

Ecosystem specific

{
    "binaries": [
        {
            "binary_name": "libxfont2",
            "binary_version": "1:2.0.1-3~ubuntu16.04.3"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-59679.json"