CVE-2020-1027

What Role Does This Play Alongside the Font Manager 0-Days?

A memory-corruption bug reachable via font parsing — like CVE-2020-0938 and CVE-2020-1020, also enriched on this site — grants initial code execution, but on Windows 10 that execution is confined to a restricted AppContainer sandbox. A kernel privilege-escalation bug patched in the same release cycle is exactly what an attacker would need to break out of that sandbox into full system control.

Overview

CVE-2020-1027 is an elevation-of-privilege vulnerability in the Windows kernel, caused by improper handling of objects in memory (CWE-787, out-of-bounds write), allowing a local, low-privileged attacker to execute code with elevated permissions (CVSS 3.1: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, 7.8 High). It was patched in the same April 2020 Patch Tuesday release as the Adobe Type Manager Library font-parsing 0-days.

Technical Details

The Windows kernel fails to properly validate certain objects it handles in memory, allowing a local attacker who has already achieved some level of code execution to corrupt kernel memory in a controlled way and escalate privileges — a standard kernel elevation-of-privilege pattern, and the same general bug class as the many other Windows kernel and Win32k CVEs from this era covered on this site.

Discovery

Patched as part of Microsoft's routine April 2020 Patch Tuesday release.

Exploitation Context

CISA added this CVE to KEV in May 2022 based on confirmed exploitation. Being fixed in the same Patch Tuesday cycle as the actively-exploited font-parsing 0-days, this bug is a natural candidate for the privilege-escalation half of a complete exploitation chain targeting Windows systems in that period, consistent with the general pattern (browser/document RCE plus kernel EoP) documented across multiple other 2020 vulnerabilities on this site.

Remediation

1. Apply Microsoft's April 2020 Patch Tuesday update immediately — this addresses this CVE alongside the Adobe Type Manager Library 0-days.
2. Deploy endpoint detection capable of identifying anomalous kernel-level privilege escalation activity.
3. Restrict local code execution opportunities (application allowlisting, restricted user permissions) to reduce the population of attackers who could reach this local-only vulnerability.
4. Patch the full set of April 2020 fixes together rather than cherry-picking — this bug's real-world value to an attacker depends on pairing it with an initial-access vulnerability from the same release cycle.