Remote code execution via DirectWrite heap overflow
Published Feb 25, 2021 · Updated Aug 3, 2024
Heap buffer overflow in Microsoft DirectWrite on affected Windows releases allows remote attackers to execute code via a crafted font. The fsg_ExecuteGlyph routine trusts undersized maxPoints and maxCompositePoints values in a TrueType maxp table and allocates an inadequate heap buffer. Exploitation requires a user or user-initiated application to render the font, and resulting code runs in the DirectWrite client's context.
Summary
What happened
Heap buffer overflow in Microsoft DirectWrite on affected Windows releases allows remote attackers to execute code via a crafted font. The fsg_ExecuteGlyph routine trusts undersized maxPoints and maxCompositePoints values in a TrueType maxp table and allocates an inadequate heap buffer. Exploitation requires a user or user-initiated application to render the font, and resulting code runs in the DirectWrite client's context.
The record
- CVE
- CVE-2021-24093
- Published
- Feb 25, 2021
- Updated
- Aug 3, 2024
- Vendor
- Microsoft
- Product
- Windows Server 2019
- Classifications
- T1203
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Feb 25, 2021CVE publishedPublication date reported by the CVE source.
- Aug 3, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=10.0.0 <publication
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Google Project Zero DirectWrite malformed-font proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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