CVE-2019-1117

published 2019-07-15

CVE-2019-1117: A remote code execution vulnerability exists in the way that DirectWrite handles objects in memory, aka 'DirectWrite Remote Code Execution Vulnerability'. This…

Priority P2 66 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-2019-1118, CVE-2019-1119, CVE-2019-1120, CVE-2019-1121, CVE-2019-1122, CVE-2019-1123, 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

url https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/47086.zip↗

process DWrite!t2Decode↗

command ./tx -cff↗

• → Monitor for recursive calls to DWrite!t2Decode on the call stack, particularly deep recursion chains (10+ frames) originating from DWrite!t2cParse -> DWrite!readGlyph -> DWrite!cfrIterateGlyphs -> DWrite!AdobeCFF2Snapshot -> DWrite!FontInstancer::InstanceCffTable, triggered during font instancing of OpenType variable fonts. ↗
• → The exploit is triggered via the Direct2D printing interface in Microsoft Edge: a user opening a specially crafted webpage with an embedded OpenType variable font and printing it (to PDF, XPS, or a printer) will trigger the vulnerable code path through d2d1!dxc::TextConvertor::InstanceFontResources -> DWrite!DWriteFontFace::CreateInstancedStream. ↗
• → The PoC font triggers the bug on decoding the glyph instruction stream for letter 'A' by calling a global subroutine (index 0) that recursively invokes itself via the tx_compose operator, incrementing cubeStackDepth without bounds until stack corruption occurs. Look for OpenType/CFF fonts with deeply recursive subroutine calls using the tx_compose (opcode 2) operator. ↗
• → Stack corruption manifests as an ACCESS_VIOLATION (code c0000005) within DWrite!t2Decode when cubeStackDepth exceeds CUBE_LE_STACKDEPTH (6), with cubeStackDepth values observed at 69+ in crash logs. This can be detected via crash telemetry or application verifier on dwrite.dll. ↗

• · The vulnerability is only reachable via the font instancing code path (variable fonts). The CreateInstancedStream method is not a public COM interface; the known trigger is through the Direct2D printing interface (d2d1!dxc::TextConvertor::InstanceFontResources). Other trigger paths may exist but are unconfirmed. ↗
• · Microsoft's advisory notes the exploit status as 'Publicly Disclosed: No; Exploited: No' with exploitation rated 'Less Likely' for both latest and older software releases at time of patch (July 2019). ↗

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

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