Code execution via unchecked property-buffer writes
Published Jul 8, 2026 · Updated Jul 8, 2026
Heap buffer overflow in X.Org libXfont2 before 2.0.8 allows remote authenticated users to execute code in the X server via a crafted PCF font. ComputeScaledProperties allocates a fixed 70-slot property buffer, then writes one or two slots per matched font property without checking capacity; duplicate name atoms can overrun it. Remote authenticated users must cause the X server to load the malicious font; exploitation crashes the server or runs code in its process context.
Summary
What happened
Heap buffer overflow in X.Org libXfont2 before 2.0.8 allows remote authenticated users to execute code in the X server via a crafted PCF font. ComputeScaledProperties allocates a fixed 70-slot property buffer, then writes one or two slots per matched font property without checking capacity; duplicate name atoms can overrun it. Remote authenticated users must cause the X server to load the malicious font; exploitation crashes the server or runs code in its process context.
The record
- CVE
- CVE-2026-56003
- Published
- Jul 8, 2026
- Updated
- Jul 8, 2026
- Vendor
- X.Org
- Product
- libXfont2
- Classifications
- CWE-122, T1210
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Jul 8, 2026CVE publishedPublication date reported by the CVE source.
- Jul 8, 2026Record 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=0 <2.0.8
What conditions does exploitation require?
What is affected?
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.
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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