Authenticated code execution via unchecked PCF bitmap sizes
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. pcfReadFont() sizes the repadded bitmap buffer from bitmapSizes[] supplied by the PCF file, then writes glyph data according to separately supplied metrics without cross-validating the two values. An authenticated X client must cause the server to load the malicious font; parsing alone writes attacker-controlled BITMAPS content beyond the heap allocation.
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. pcfReadFont() sizes the repadded bitmap buffer from bitmapSizes[] supplied by the PCF file, then writes glyph data according to separately supplied metrics without cross-validating the two values. An authenticated X client must cause the server to load the malicious font; parsing alone writes attacker-controlled BITMAPS content beyond the heap allocation.
The record
- CVE
- CVE-2026-56002
- Published
- Jul 8, 2026
- Updated
- Jul 8, 2026
- Vendor
- X.Org
- Product
- libXfont2
- Classifications
- CWE-122, CAPEC-234, T1068
- 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?
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- 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.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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