Bug 2497343 (CVE-2026-59691)

Summary:	CVE-2026-59691 gstreamer: gstreamer: rfbsrc/librfb Hextile heap out-of-bounds write with 16bpp framebuffer
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	rhel-process-autobot, security-response-team, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A heap buffer overflow vulnerability was found in GStreamer's rfbsrc plugin. When a client connects to a malicious RFB/VNC server that advertises a 16bpp framebuffer and sends Hextile-encoded updates, the Hextile background fill path writes 32-bit pixel values into a buffer allocated for 16-bit pixels. This type mismatch causes an out-of-bounds heap write that can lead to denial of service (process crash) and potential memory corruption.	Story Points:	---
Clone Of:		Environment:
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Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-07-06 13:42:12 UTC

A heap buffer overflow was found in GStreamer's rfbsrc plugin (gst-plugins-bad, librfb component). In rfb_decoder_fill_rectangle(), when a malicious RFB/VNC server advertises a 16bpp RGB565 framebuffer and sends a Hextile-encoded update, the background fill path computes the destination offset using decoder->bytespp (2 bytes) but casts the destination to guint32* and writes one 32-bit value per pixel. For bytespp == 2, the framebuffer is allocated as 2 bytes per pixel, but the fill loop writes and advances by 4 bytes per pixel, causing a heap out-of-bounds write.

File: subprojects/gst-plugins-bad/gst/librfb/rfbdecoder.c
Function: rfb_decoder_fill_rectangle()

A remote attacker controlling an RFB/VNC server can trigger this by having a client connect using rfbsrc. The demonstrated impact is heap-buffer-overflow and process abort. Since this is a heap out-of-bounds write on remote input, integrity impact is possible though code execution has not been demonstrated.

Affected: GStreamer gst-plugins-bad (reproduced on 1.28.3)
Fixed: Planned for GStreamer 1.28.5
Fix MR: https://gitlab.freedesktop.org/gstreamer/gstreamer-security/-/merge_requests/100
Upstream issue: https://gitlab.freedesktop.org/gstreamer/gstreamer/-/work_items/5173 (confidential)
Advisory: GST-SA-2026-0063

Reporter: Clouditera Security; Z.ai Security; NSFOCUS
PSIRT Ticket: PSIRTSUPT-19089

Comment 1 errata-xmlrpc 2026-07-28 19:43:47 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:47180 https://access.redhat.com/errata/RHSA-2026:47180

Comment 2 errata-xmlrpc 2026-07-29 02:02:08 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:47179 https://access.redhat.com/errata/RHSA-2026:47179

Comment 3 errata-xmlrpc 2026-07-29 07:20:43 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:47731 https://access.redhat.com/errata/RHSA-2026:47731

Comment 4 errata-xmlrpc 2026-08-13 16:39:14 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10.0 Extended Update Support

Via RHSA-2026:54659 https://access.redhat.com/errata/RHSA-2026:54659

Comment 5 errata-xmlrpc 2026-08-13 18:04:33 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.6 Extended Update Support

Via RHSA-2026:54660 https://access.redhat.com/errata/RHSA-2026:54660

Comment 6 errata-xmlrpc 2026-08-13 18:08:32 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions

Via RHSA-2026:54658 https://access.redhat.com/errata/RHSA-2026:54658

Comment 7 errata-xmlrpc 2026-08-13 18:11:22 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-2026:54665 https://access.redhat.com/errata/RHSA-2026:54665

Comment 8 errata-xmlrpc 2026-08-13 18:17:11 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-2026:54664 https://access.redhat.com/errata/RHSA-2026:54664

Comment 9 errata-xmlrpc 2026-08-14 00:07:10 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7 Extended Lifecycle Support

Via RHSA-2026:54752 https://access.redhat.com/errata/RHSA-2026:54752

Comment 10 errata-xmlrpc 2026-08-19 03:48:19 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:56658 https://access.redhat.com/errata/RHSA-2026:56658

Comment 11 errata-xmlrpc 2026-08-19 05:28:08 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-2026:56772 https://access.redhat.com/errata/RHSA-2026:56772

Comment 12 errata-xmlrpc 2026-09-02 08:55:48 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7 Extended Lifecycle Support

Via RHSA-2026:62532 https://access.redhat.com/errata/RHSA-2026:62532