Bug 2419870 (CVE-2025-40304)

Summary:	CVE-2025-40304 kernel: Linux kernel: Out-of-bounds write in fbdev can lead to privilege escalation, information disclosure, or denial of service.
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	Keywords:	Security
Target Milestone:	---
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel, specifically within the framebuffer device (fbdev) subsystem. This vulnerability, an out-of-bounds write, occurs because the `bit_putcs` function does not properly check boundaries when displaying text near the edges of the screen. A local user with low privileges could exploit this to write data beyond the intended memory area. This could potentially lead to serious consequences such as gaining unauthorized access (privilege escalation), revealing sensitive information (information disclosure), or causing the system to become unavailable (denial of service).	Story Points:	---
Clone Of:		Environment:
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Regression:	---	Mount Type:	---
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Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2025-12-08 07:04:51 UTC

In the Linux kernel, the following vulnerability has been resolved:

fbdev: Add bounds checking in bit_putcs to fix vmalloc-out-of-bounds

Add bounds checking to prevent writes past framebuffer boundaries when
rendering text near screen edges. Return early if the Y position is off-screen
and clip image height to screen boundary. Break from the rendering loop if the
X position is off-screen. When clipping image width to fit the screen, update
the character count to match the clipped width to prevent buffer size
mismatches.

Without the character count update, bit_putcs_aligned and bit_putcs_unaligned
receive mismatched parameters where the buffer is allocated for the clipped
width but cnt reflects the original larger count, causing out-of-bounds writes.

Comment 1 Jon Moroney 2025-12-08 23:42:28 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025120820-CVE-2025-40304-47b3@gregkh/T

Comment 4 errata-xmlrpc 2026-02-02 15:25:22 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10.0 Extended Update Support

Via RHSA-2026:1727 https://access.redhat.com/errata/RHSA-2026:1727

Comment 8 errata-xmlrpc 2026-02-09 09:31:59 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:2282 https://access.redhat.com/errata/RHSA-2026:2282

Comment 9 errata-xmlrpc 2026-02-11 00:16:06 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 Update Services for SAP Solutions
  Red Hat Enterprise Linux 8.6 Telecommunications Update Service

Via RHSA-2026:2490 https://access.redhat.com/errata/RHSA-2026:2490

Comment 10 errata-xmlrpc 2026-02-11 11:50:57 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-2026:2535 https://access.redhat.com/errata/RHSA-2026:2535

Comment 11 errata-xmlrpc 2026-02-11 14:34:05 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:2560 https://access.redhat.com/errata/RHSA-2026:2560

Comment 12 errata-xmlrpc 2026-02-11 16:30:37 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions

Via RHSA-2026:2573 https://access.redhat.com/errata/RHSA-2026:2573

Comment 13 errata-xmlrpc 2026-02-11 17:04:15 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions

Via RHSA-2026:2577 https://access.redhat.com/errata/RHSA-2026:2577

Comment 14 errata-xmlrpc 2026-02-11 17:45:04 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:2583 https://access.redhat.com/errata/RHSA-2026:2583

Comment 15 errata-xmlrpc 2026-02-12 15:12:33 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.2 Advanced Update Support

Via RHSA-2026:2664 https://access.redhat.com/errata/RHSA-2026:2664

Comment 16 errata-xmlrpc 2026-02-16 11:50:22 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:2720 https://access.redhat.com/errata/RHSA-2026:2720

Comment 17 errata-xmlrpc 2026-02-16 12:02:45 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:2722 https://access.redhat.com/errata/RHSA-2026:2722

Comment 18 errata-xmlrpc 2026-02-16 17:27:33 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.6 Extended Update Support

Via RHSA-2026:2759 https://access.redhat.com/errata/RHSA-2026:2759

Comment 19 errata-xmlrpc 2026-02-17 00:43:07 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.4 Extended Update Support

Via RHSA-2026:2766 https://access.redhat.com/errata/RHSA-2026:2766

Comment 20 errata-xmlrpc 2026-02-17 12:46:28 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:2821 https://access.redhat.com/errata/RHSA-2026:2821

Comment 21 errata-xmlrpc 2026-02-25 15:16:43 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-2026:3360 https://access.redhat.com/errata/RHSA-2026:3360