CVE-2019-1123

published 2019-07-15

CVE-2019-1123: A remote code execution vulnerability exists in the way that DirectWrite handles objects in memory, aka 'DirectWrite Remote Code Execution Vulnerability'. This…

Priority P2 65 high 8.8 CVSS 3.0

AV N AC L PR N UI R S U C H I H A H

EXPLOIT

A remote code execution vulnerability exists in the way that DirectWrite handles objects in memory, aka 'DirectWrite Remote Code Execution Vulnerability'. This CVE ID is unique from CVE-2019-1117, CVE-2019-1118, CVE-2019-1119, CVE-2019-1120, CVE-2019-1121, CVE-2019-1122, CVE-2019-1124, CVE-2019-1127, CVE-2019-1128.

Affected

36 ranges · showing 25

Vendor	Product	Version range	Fixed in
microsoft	windows	—	—
microsoft	windows	—	—
microsoft	windows	—	—
microsoft	windows	—	—
microsoft	windows	—	—
microsoft	windows	—	—
microsoft	windows	—	—
microsoft	windows	—	—
microsoft	windows	—	—
microsoft	windows_10	—	—
microsoft	windows_10	—	—
microsoft	windows_10	—	—
microsoft	windows_10	—	—
microsoft	windows_10_version_1903_for_32-bit_systems	—	—
microsoft	windows_10_version_1903_for_arm64-based_systems	—	—
microsoft	windows_10_version_1903_for_x64-based_systems	—	—
microsoft	windows_server	—	—
microsoft	windows_server	—	—
microsoft	windows_server	—	—
microsoft	windows_server_2016	—	—
microsoft	windows_server_2016	—	—
msrc	windows_10_version_1709_for_32-bit_systems	—	—
msrc	windows_10_version_1709_for_arm64-based_systems	—	—
msrc	windows_10_version_1709_for_x64-based_systems	—	—
msrc	windows_10_version_1803_for_32-bit_systems	—	—

Detection & IOCs extracted from sources · hover to see the quote

filename poc.otf↗

command ./tx -cff poc.otf↗

• → Look for OpenType font files (.otf) containing both a 'CFF ' table and a 'CFF2' table simultaneously — the PoC inserts a malicious CFF table alongside a legitimate CFF2 table to trigger the vulnerable AFDKO code path in DirectWrite. ↗
• → The exploit is triggered via the Direct2D printing interface in Microsoft Edge — monitor for Edge renderer process crashes (access violation c0000005) in DWrite!handleBlend when a user prints a webpage containing an embedded OpenType variable font. ↗
• → The malicious font's Private DICT begins with a cff_longint value of 0x31313131 followed by a cff_blend operator — look for CFF fonts with numBlends set to 0x31313131 (825307441) as a specific PoC indicator. ↗
• → Monitor for access violation exceptions (code c0000005) in the Edge renderer process (MicrosoftEdgeCP.exe) originating from DWrite!handleBlend, which indicates exploitation of this vulnerability. ↗

• · The vulnerability is only reachable through the font instancing code path (dwrite!AdobeCFF2Snapshot via FontInstancer), which is triggered specifically when printing variable fonts — not during normal font rendering. The attack surface is limited to the Direct2D printing interface. ↗

CVSS provenance

nvd v3.0 8.8 HIGH CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

nvd v2.0 9.3 CRITICAL AV:N/AC:M/Au:N/C:C/I:C/A:C

vendor_msrc 7.8 HIGH

CVEs like this are exactly what “Exploited This Week” covers.

Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.