CVE intelligence

CVE-2026-44950

Vulnerability intelligence

Published Sep 10, 2026Sources checked Nov 10, 2026

9.0CRITICALCVSS out of 10

What this means

Review the available evidence

CVE-2026-44950 and is rated Critical severity with a CVSS score of 9.0. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Microsoft Security Response Center guidance

Vendor revision: Sep 19, 2026

See the Microsoft Security Update Guide for the update that applies to your product.

Vendor-listed releases

2.0.9-1

CISA KEVNot listedBased on the latest collected catalog

EPSS0.3%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-44950?

fs_read_glyphs() in the libXfont2 font-server client (src/fc/fserve.c) copies each glyph's bitmap into a single buffer. Existing checks validates only that the source slice (position, length) lies within the source bitmap buffer.

It does not check whether the running destination cursor has exceeded the allocation.

A malicious font server can send overlapping source offsets -- for example 1000 glyphs each referencing {position:0, length:64} with nbytes=64. Each individual source range passes the existing validation, but the cumulative writes total 64000 bytes into a 64-byte destination buffer.

This is a heap buffer overflow with attacker-controlled content.

Source: NVD