Bug 2496641 (CVE-2026-56002) - CVE-2026-56002 libXfont2: PCF Font Parsing Heap Buffer Overflow
Summary: CVE-2026-56002 libXfont2: PCF Font Parsing Heap Buffer Overflow
Keywords:
Status: NEW
Alias: CVE-2026-56002
Deadline: 2026-07-08
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-07-02 18:36 UTC by OSIDB Bzimport
Modified: 2026-08-06 12:46 UTC (History)
5 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2026:47079 0 None None None 2026-07-28 13:52:42 UTC
Red Hat Product Errata RHSA-2026:47084 0 None None None 2026-07-29 00:27:25 UTC
Red Hat Product Errata RHSA-2026:47103 0 None None None 2026-07-28 21:14:50 UTC
Red Hat Product Errata RHSA-2026:51058 0 None None None 2026-08-06 12:27:10 UTC
Red Hat Product Errata RHSA-2026:51059 0 None None None 2026-08-06 12:43:16 UTC
Red Hat Product Errata RHSA-2026:51060 0 None None None 2026-08-06 12:04:53 UTC
Red Hat Product Errata RHSA-2026:51061 0 None None None 2026-08-06 11:54:05 UTC
Red Hat Product Errata RHSA-2026:51062 0 None None None 2026-08-06 12:08:38 UTC
Red Hat Product Errata RHSA-2026:51063 0 None None None 2026-08-06 12:34:10 UTC
Red Hat Product Errata RHSA-2026:51066 0 None None None 2026-08-06 12:46:35 UTC
Red Hat Product Errata RHSA-2026:51067 0 None None None 2026-08-06 12:33:43 UTC

Description OSIDB Bzimport 2026-07-02 18:36:08 UTC 
In libXfont2's pcfReadFont() function, the repadded bitmap buffer is allocated using a bitmapSizes[] value read directly from the PCF file without cross-validation against per-glyph metrics. Writing to that array uses the per-glyph metrics from the file also without validation. A malicious PCF font can declare a tiny bitmapSizes[] value (e.g. 16 bytes) for the server's glyph pad index and a per-glyph metrics that exceeds this size, causing a write past the end of the allocation with attacker-controlled content from the PCF BITMAPS payload. No rendering is needed -- the overflow occurs during font parsing itself.
Comment 5 Tomas Hoger 2026-07-28 07:36:26 UTC 
Upstream advisory:
https://www.openwall.com/lists/oss-security/2026/07/08/1

Upstream commit:
https://gitlab.freedesktop.org/xorg/lib/libxfont/-/commit/b4389e0b1d84a690b819bb27b1439968811a3674
Comment 6 errata-xmlrpc 2026-07-28 13:52:41 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:47079 https://access.redhat.com/errata/RHSA-2026:47079
Comment 7 errata-xmlrpc 2026-07-28 21:14:49 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:47103 https://access.redhat.com/errata/RHSA-2026:47103
Comment 8 errata-xmlrpc 2026-07-29 00:27:24 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:47084 https://access.redhat.com/errata/RHSA-2026:47084
Comment 26 errata-xmlrpc 2026-08-06 11:54:04 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10.0 Extended Update Support

Via RHSA-2026:51061 https://access.redhat.com/errata/RHSA-2026:51061
Comment 27 errata-xmlrpc 2026-08-06 12:04:52 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
  Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On

Via RHSA-2026:51060 https://access.redhat.com/errata/RHSA-2026:51060
Comment 28 errata-xmlrpc 2026-08-06 12:08:37 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:51062 https://access.redhat.com/errata/RHSA-2026:51062
Comment 29 errata-xmlrpc 2026-08-06 12:27:09 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions

Via RHSA-2026:51058 https://access.redhat.com/errata/RHSA-2026:51058
Comment 30 errata-xmlrpc 2026-08-06 12:33:42 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
  Red Hat Enterprise Linux 8.8 Telecommunications Update Service

Via RHSA-2026:51067 https://access.redhat.com/errata/RHSA-2026:51067
Comment 31 errata-xmlrpc 2026-08-06 12:34:09 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7 Extended Lifecycle Support

Via RHSA-2026:51063 https://access.redhat.com/errata/RHSA-2026:51063
Comment 32 errata-xmlrpc 2026-08-06 12:43:16 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.6 Extended Update Support

Via RHSA-2026:51059 https://access.redhat.com/errata/RHSA-2026:51059
Comment 33 errata-xmlrpc 2026-08-06 12:46:34 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
  Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On

Via RHSA-2026:51066 https://access.redhat.com/errata/RHSA-2026:51066
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