CVE-2026-56001Network attack vector

Authenticated code execution via wrapped bitmap allocation

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. BitmapScaleBitmaps stores the allocation size in a 32-bit variable; inflated per-glyph byte counts wrap it, so calloc reserves too little space for later writes. Exploitation requires X server access plus SetFontPath and OpenFont requests using a crafted PCF font and an inflationary scale factor.

CVSS severity8.8
High
EPSS probability0.39%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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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. BitmapScaleBitmaps stores the allocation size in a 32-bit variable; inflated per-glyph byte counts wrap it, so calloc reserves too little space for later writes. Exploitation requires X server access plus SetFontPath and OpenFont requests using a crafted PCF font and an inflationary scale factor.

The record

CVE
CVE-2026-56001
Published
Jul 8, 2026
Updated
Jul 8, 2026
Vendor
X.Org
Product
libXfont2
Classifications
CWE-122, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 8, 2026CVE publishedPublication date reported by the CVE source.
  2. 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.

  1. Affected versionversion=0 <2.0.8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

X.Org · libXfont2version=0 <2.0.8

Published CVSS scores

8.5SUSECVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
8.8NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

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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