CVE-2026-59679 libXfont2 - Out-of-Bounds Read & Write

libXfont2 font-server client contains a heap out-of-bounds read and write caused by inconsistent size checks between FS_QueryXExtents16 and FS_QueryXBitmaps16 replies, letting a malicious font server perform memory corruption remotely, exploit requires a malicious or compromised font server.

CVSS base score 9.0 /10
Critical
CISA KEV
Not listed
Public exploit
None known
EPSS
0.26% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Out-of-Bounds Read
Impact
Remote Code Execution, Denial Of Service
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Published
10 September 2026
Updated
15 October 2026
Weakness
CWE-787

Vendor fix

Update to the latest version with proper bounds checking between FS_QueryXExtents16 and FS_QueryXBitmaps16 replies.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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