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Vulnerability record · CVE-2020-1020 · published 15 April 2020

CVE-2020-1020: Windows Adobe Type Manager Library font parsing out-of-bounds write RCE

Microsoft · Windows 10 1507

Microsoft Windows Adobe Type Manager Library mishandles a specially crafted multi-master font in Adobe Type 1 PostScript format, causing an out-of-bounds write (CWE-787). Successful exploitation allows remote code execution, and the flaw affects a broad set of Windows client and server versions. It matters because it is a remotely reachable memory corruption bug in a core font parsing component.

8.8 CVSS 3.1 High CISA KEV since 3 Nov 2021 EPSS 65% · top 0.8% CWE-787 · Out-of-bounds write
8.8CVSS 3.1 base score, v2 6.8
65%EPSS exploitation probability, 30 days
YesIn CISA KEV, fix deadline passed
16Affected product versions listed by NVD
3References
17 Jun 2026Last modified by NVD

Description

A remote code execution vulnerability exists in Microsoft Windows when the Windows Adobe Type Manager Library improperly handles a specially-crafted multi-master font - Adobe Type 1 PostScript format.For all systems except Windows 10, an attacker who successfully exploited the vulnerability could execute code remotely, aka 'Adobe Font Manager Library Remote Code Execution Vulnerability'. This CVE ID is unique from CVE-2020-0938.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 17 September 2026. Confidence: high.

critical priorityIt is a network-reachable remote code execution flaw in a widely deployed Windows component, listed in CISA KEV with very high EPSS, and affects many supported and legacy Windows versions.

What it is

Microsoft Windows Adobe Type Manager Library mishandles a specially crafted multi-master font in Adobe Type 1 PostScript format, causing an out-of-bounds write (CWE-787). Successful exploitation allows remote code execution, and the flaw affects a broad set of Windows client and server versions. It matters because it is a remotely reachable memory corruption bug in a core font parsing component.

Impact

An attacker who exploits the flaw can execute arbitrary code in the context of the affected process, potentially taking control of the system. On systems other than Windows 10, the description states code can be executed remotely.

Attack surface

The vector is network-reachable (AV:N) with no privileges required (PR:N) but requires user interaction (UI:R), consistent with a victim opening or previewing a crafted font file. No authentication is needed, but the victim must trigger parsing of the malicious font.

Exploitation

The vulnerability is listed in CISA KEV (added 2021-11-03) and has a high EPSS 30-day probability of 0.65037 (99.21st percentile), indicating observed exploitation activity. No ransomware campaign use is documented in the record.

What to do

  • Apply the Microsoft security update referenced in the vendor advisory for all affected Windows versions.
  • Prioritize patching internet-facing and user-workstation systems, including Windows 7, 8.1, RT 8.1, Server 2008/2012/2016/2019, and Windows 10 builds listed.
  • Restrict or block untrusted font file delivery via email and web downloads where feasible.
  • Disable or harden font preview/rendering paths in applications that process untrusted documents if patching cannot be completed immediately.

Detection

  • Monitor for processes loading or parsing Adobe Type 1 PostScript font files from untrusted locations, especially unusual file paths or email attachment directories.
  • Hunt for crashes or abnormal terminations in font-related Windows components (e.g., ATMFD/font parsing) that may indicate exploitation attempts.
  • Review endpoint telemetry for suspicious child processes spawned by document viewers, browsers, or font rendering services.
  • Correlate KEV/EPSS signals with asset inventory to confirm patched status on all affected Windows versions.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.

Exploitation in the wild

CISA added CVE-2020-1020 to the Known Exploited Vulnerabilities catalog on 3 November 2021 as "Microsoft Windows Adobe Font Manager Library Remote Code Execution Vulnerability". Required action: Apply updates per vendor instructions. Federal deadline 3 May 2022.

Affected products

16 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1020 PatchVendor Advisory
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1020 PatchVendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-1020 US Government Resource

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Source: NIST National Vulnerability Database (record CVE-2020-1020), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.