CVE-2026-34001

A flaw was found in the X.Org X server. This use-after-free vulnerability occurs in the XSYNC fence triggering logic, specifically within the miSyncTriggerFence() function. An attacker with access to the X11 server can exploit this without user interaction, leading to a server crash and potentially enabling memory corruption. This could result in a denial of service or further compromise of the system.

X.Org X11 X server

Security Fix(es):

A flaw was found in the X.Org X server. This integer underflow vulnerability, specifically in the XKB compatibility map handling, allows an attacker with local or remote X11 server access to trigger a buffer read overrun. This can lead to memory-safety violations and potentially a denial of service (DoS) or other severe impacts.(CVE-2026-33999)

(CVE-2026-34000)

A flaw was found in the X.Org X server. This use-after-free vulnerability occurs in the XSYNC fence triggering logic, specifically within the miSyncTriggerFence() function. An attacker with access to the X11 server can exploit this without user interaction, leading to a server crash and potentially enabling memory corruption. This could result in a denial of service or further compromise of the system.(CVE-2026-34001)

(CVE-2026-34002)

A flaw was found in the X.Org X server's XKB key types request validation. A local attacker could send a specially crafted request to the X server, leading to an out-of-bounds memory access vulnerability. This could result in the disclosure of sensitive information or cause the server to crash, leading to a Denial of Service (DoS). In certain configurations, higher impact outcomes may be possible.(CVE-2026-34003)

Xwayland is an X server for running X clients under Wayland. %package devel Summary: Development package Requires: pkgconfig %description devel The development package provides the developmental files which are necessary for developing Wayland compositors using Xwayland. %prep %autosetup -n xwayland- -p1 %build %meson \ -Ddefault_font_path="catalogue:/etc/X11/fontpath.d,built-ins" \ -Dbuilder_string="Build ID: -" \ -Dxkb_output_dir=/lib/xkb \ -Dxcsecurity=true \ -Dglamor=true \ -Ddri3=true %meson_build

Security Fix(es):

A flaw was found in the X.Org X server and Xwayland when processing X11 Present extension notifications. Improper error handling during notification creation can leave dangling pointers that lead to a use-after-free condition. This can cause memory corruption or a crash, potentially allowing an attacker to execute arbitrary code or cause a denial of service.(CVE-2025-62229)

A flaw was identified in the X.Org X server’s X Keyboard (Xkb) extension where improper bounds checking in the XkbSetCompatMap() function can cause an unsigned short overflow. If an attacker sends specially crafted input data, the value calculation may overflow, leading to memory corruption or a crash.(CVE-2025-62231)

A flaw was found in the X.Org X server. This integer underflow vulnerability, specifically in the XKB compatibility map handling, allows an attacker with local or remote X11 server access to trigger a buffer read overrun. This can lead to memory-safety violations and potentially a denial of service (DoS) or other severe impacts.(CVE-2026-33999)

A flaw was found in the X.Org X server. This use-after-free vulnerability occurs in the XSYNC fence triggering logic, specifically within the miSyncTriggerFence() function. An attacker with access to the X11 server can exploit this without user interaction, leading to a server crash and potentially enabling memory corruption. This could result in a denial of service or further compromise of the system.(CVE-2026-34001)

A flaw was found in the X.Org X server. This vulnerability, an out-of-bounds read, affects the XKB (X Keyboard Extension) modifier map handling. An attacker with access to the X11 server can exploit this by sending a malformed request, which causes the server to read beyond its intended memory boundaries. This can lead to the exposure of sensitive information or cause the server to crash, resulting in a denial of service.(CVE-2026-34002)

A flaw was found in the X.Org X server's XKB key types request validation. A local attacker could send a specially crafted request to the X server, leading to an out-of-bounds memory access vulnerability. This could result in the disclosure of sensitive information or cause the server to crash, leading to a Denial of Service (DoS). In certain configurations, higher impact outcomes may be possible.(CVE-2026-34003)

['Hi all,\n\nCVEs have been issued now, please see inline below\n\nOn Tue, Jun 02, 2026 at 10:01:46AM +1000, Peter Hutterer wrote:', "=======================================================================\nX.Org Security Advisory: June 2, 2026 \n\nIssues in X.Org X server prior to 21.1.23 and Xwayland prior to 24.1.12\n=======================================================================\n\nMultiple issues have been found in the X server and Xwayland implementations\npublished by X.Org for which we are releasing security fixes for in\nxorg-server-21.1.23 and xwayland-24.1.12.\n\nNote that CVEs have been requested for these issues but did not get assigned in\ntime for this disclosure.\n\n* Font Alias Stack-based Buffer Overflow\n\n A mismatch between the X server and the libXfont2 library's maximum\n font name length can cause a stack buffer overflow during font alias\n resolution. The server allocates a 256 byte stack buffer but libXfont2's\n alias target name length is 1024 bytes.…

Xwayland is an X server for running X clients under Wayland. %package devel Summary: Development package Requires: pkgconfig %description devel The development package provides the developmental files which are necessary for developing Wayland compositors using Xwayland. %prep %autosetup -n xwayland- -p1 %build %meson \ -Ddefault_font_path="catalogue:/etc/X11/fontpath.d,built-ins" \ -Dbuilder_string="Build ID: -" \ -Dxkb_output_dir=/lib/xkb \ -Dxcsecurity=true \ -Dglamor=true \ -Ddri3=true %meson_build

Security Fix(es):

A flaw was found in the X.Org X server and Xwayland when processing X11 Present extension notifications. Improper error handling during notification creation can leave dangling pointers that lead to a use-after-free condition. This can cause memory corruption or a crash, potentially allowing an attacker to execute arbitrary code or cause a denial of service.(CVE-2025-62229)

A flaw was identified in the X.Org X server’s X Keyboard (Xkb) extension where improper bounds checking in the XkbSetCompatMap() function can cause an unsigned short overflow. If an attacker sends specially crafted input data, the value calculation may overflow, leading to memory corruption or a crash.(CVE-2025-62231)

A flaw was found in the X.Org X server. This integer underflow vulnerability, specifically in the XKB compatibility map handling, allows an attacker with local or remote X11 server access to trigger a buffer read overrun. This can lead to memory-safety violations and potentially a denial of service (DoS) or other severe impacts.(CVE-2026-33999)

A flaw was found in the X.Org X server. This use-after-free vulnerability occurs in the XSYNC fence triggering logic, specifically within the miSyncTriggerFence() function. An attacker with access to the X11 server can exploit this without user interaction, leading to a server crash and potentially enabling memory corruption. This could result in a denial of service or further compromise of the system.(CVE-2026-34001)

A flaw was found in the X.Org X server. This vulnerability, an out-of-bounds read, affects the XKB (X Keyboard Extension) modifier map handling. An attacker with access to the X11 server can exploit this by sending a malformed request, which causes the server to read beyond its intended memory boundaries. This can lead to the exposure of sensitive information or cause the server to crash, resulting in a denial of service.(CVE-2026-34002)

A flaw was found in the X.Org X server's XKB key types request validation. A local attacker could send a specially crafted request to the X server, leading to an out-of-bounds memory access vulnerability. This could result in the disclosure of sensitive information or cause the server to crash, leading to a Denial of Service (DoS). In certain configurations, higher impact outcomes may be possible.(CVE-2026-34003)

['Hi all,\n\nCVEs have been issued now, please see inline below\n\nOn Tue, Jun 02, 2026 at 10:01:46AM +1000, Peter Hutterer wrote:', "=======================================================================\nX.Org Security Advisory: June 2, 2026 \n\nIssues in X.Org X server prior to 21.1.23 and Xwayland prior to 24.1.12\n=======================================================================\n\nMultiple issues have been found in the X server and Xwayland implementations\npublished by X.Org for which we are releasing security fixes for in\nxorg-server-21.1.23 and xwayland-24.1.12.\n\nNote that CVEs have been requested for these issues but did not get assigned in\ntime for this disclosure.\n\n* Font Alias Stack-based Buffer Overflow\n\n A mismatch between the X server and the libXfont2 library's maximum\n font name length can cause a stack buffer overflow during font alias\n resolution. The server allocates a 256 byte stack buffer but libXfont2's\n alias target name length is 1024 bytes.…

Xwayland is an X server for running X clients under Wayland. %package devel Summary: Development package Requires: pkgconfig %description devel The development package provides the developmental files which are necessary for developing Wayland compositors using Xwayland. %prep %autosetup -n xwayland- -p1 %build %meson \ -Ddefault_font_path="catalogue:/etc/X11/fontpath.d,built-ins" \ -Dbuilder_string="Build ID: -" \ -Dxkb_output_dir=/lib/xkb \ -Dxcsecurity=true \ -Dglamor=true \ -Ddri3=true %meson_build

Security Fix(es):

A flaw was found in the X.Org X server and Xwayland when processing X11 Present extension notifications. Improper error handling during notification creation can leave dangling pointers that lead to a use-after-free condition. This can cause memory corruption or a crash, potentially allowing an attacker to execute arbitrary code or cause a denial of service.(CVE-2025-62229)

A flaw was identified in the X.Org X server’s X Keyboard (Xkb) extension where improper bounds checking in the XkbSetCompatMap() function can cause an unsigned short overflow. If an attacker sends specially crafted input data, the value calculation may overflow, leading to memory corruption or a crash.(CVE-2025-62231)

A flaw was found in the X.Org X server. This integer underflow vulnerability, specifically in the XKB compatibility map handling, allows an attacker with local or remote X11 server access to trigger a buffer read overrun. This can lead to memory-safety violations and potentially a denial of service (DoS) or other severe impacts.(CVE-2026-33999)

A flaw was found in the X.Org X server. This use-after-free vulnerability occurs in the XSYNC fence triggering logic, specifically within the miSyncTriggerFence() function. An attacker with access to the X11 server can exploit this without user interaction, leading to a server crash and potentially enabling memory corruption. This could result in a denial of service or further compromise of the system.(CVE-2026-34001)

A flaw was found in the X.Org X server. This vulnerability, an out-of-bounds read, affects the XKB (X Keyboard Extension) modifier map handling. An attacker with access to the X11 server can exploit this by sending a malformed request, which causes the server to read beyond its intended memory boundaries. This can lead to the exposure of sensitive information or cause the server to crash, resulting in a denial of service.(CVE-2026-34002)

A flaw was found in the X.Org X server's XKB key types request validation. A local attacker could send a specially crafted request to the X server, leading to an out-of-bounds memory access vulnerability. This could result in the disclosure of sensitive information or cause the server to crash, leading to a Denial of Service (DoS). In certain configurations, higher impact outcomes may be possible.(CVE-2026-34003)

['Hi all,\n\nCVEs have been issued now, please see inline below\n\nOn Tue, Jun 02, 2026 at 10:01:46AM +1000, Peter Hutterer wrote:', "=======================================================================\nX.Org Security Advisory: June 2, 2026 \n\nIssues in X.Org X server prior to 21.1.23 and Xwayland prior to 24.1.12\n=======================================================================\n\nMultiple issues have been found in the X server and Xwayland implementations\npublished by X.Org for which we are releasing security fixes for in\nxorg-server-21.1.23 and xwayland-24.1.12.\n\nNote that CVEs have been requested for these issues but did not get assigned in\ntime for this disclosure.\n\n* Font Alias Stack-based Buffer Overflow\n\n A mismatch between the X server and the libXfont2 library's maximum\n font name length can cause a stack buffer overflow during font alias\n resolution. The server allocates a 256 byte stack buffer but libXfont2's\n alias target name length is 1024 bytes.…

Virtual Network Computing (VNC) is a remote display system which allows users to view a computing desktop environment not only on the machine where it is running, but from anywhere on the Internet and from a wide variety of machine architectures. TigerVNC is a suite of VNC servers and clients.

Security Fix(es):

• xorg: xwayland: X.Org X server: Denial of Service via integer underflow in XKB compatibility map handling (CVE-2026-33999)

• xorg: xwayland: X.Org X server: Use-after-free vulnerability leads to server crash and potential memory corruption (CVE-2026-34001)

• xorg: xwayland: X.Org X server: Information exposure and denial of service via out-of-bounds memory access (CVE-2026-34003)

• TigerVNC: x0vncserver: TigerVNC x0vncserver: Information disclosure, data manipulation, and denial of service via incorrect permissions (CVE-2026-34352)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Xwayland is an X server for running X clients under Wayland.

Security Fix(es):

• xorg: xwayland: X.Org X server: Denial of Service via integer underflow in XKB compatibility map handling (CVE-2026-33999)

• xorg: xwayland: X.Org X server: Use-after-free vulnerability leads to server crash and potential memory corruption (CVE-2026-34001)

• xorg: xwayland: X.Org X server: Information exposure and denial of service via out-of-bounds memory access (CVE-2026-34003)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Xwayland is an X server for running X clients under Wayland.

Security Fix(es):

• xorg: xwayland: X.Org X server: Denial of Service via integer underflow in XKB compatibility map handling (CVE-2026-33999)

• xorg: xwayland: X.Org X server: Use-after-free vulnerability leads to server crash and potential memory corruption (CVE-2026-34001)

• xorg: xwayland: X.Org X server: Information exposure and denial of service via out-of-bounds memory access (CVE-2026-34003)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

X.Org is an open-source implementation of the X Window System. It provides the basic low-level functionality that full-fledged graphical user interfaces are designed upon.

Security Fix(es):

• xorg: xwayland: X.Org X server: Denial of Service via integer underflow in XKB compatibility map handling (CVE-2026-33999)

• xorg: xwayland: X.Org X server: Use-after-free vulnerability leads to server crash and potential memory corruption (CVE-2026-34001)

• xorg: xwayland: X.Org X server: Information exposure and denial of service via out-of-bounds memory access (CVE-2026-34003)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Xwayland is an X server for running X clients under Wayland.

Security Fix(es):

• xorg: xwayland: X.Org X server: Denial of Service via integer underflow in XKB compatibility map handling (CVE-2026-33999)

• xorg: xwayland: X.Org X server: Use-after-free vulnerability leads to server crash and potential memory corruption (CVE-2026-34001)

• xorg: xwayland: X.Org X server: Information exposure and denial of service via out-of-bounds memory access (CVE-2026-34003)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

X.Org is an open-source implementation of the X Window System. It provides the basic low-level functionality that full-fledged graphical user interfaces are designed upon.

Security Fix(es):

• xorg: xwayland: X.Org X server: Denial of Service via integer underflow in XKB compatibility map handling (CVE-2026-33999)

• xorg: xwayland: X.Org X server: Use-after-free vulnerability leads to server crash and potential memory corruption (CVE-2026-34001)

• xorg: xwayland: X.Org X server: Information exposure and denial of service via out-of-bounds memory access (CVE-2026-34003)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Virtual Network Computing (VNC) is a remote display system which allows users to view a computing desktop environment not only on the machine where it is running, but from anywhere on the Internet and from a wide variety of machine architectures. TigerVNC is a suite of VNC servers and clients.

Security Fix(es):

• xorg: xwayland: X.Org X server: Denial of Service via integer underflow in XKB compatibility map handling (CVE-2026-33999)

• xorg: xwayland: X.Org X server: Use-after-free vulnerability leads to server crash and potential memory corruption (CVE-2026-34001)

• xorg: xwayland: X.Org X server: Information exposure and denial of service via out-of-bounds memory access (CVE-2026-34003)

• TigerVNC: x0vncserver: TigerVNC x0vncserver: Information disclosure, data manipulation, and denial of service via incorrect permissions (CVE-2026-34352)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Xwayland is an X server for running X clients under Wayland.

Security Fix(es):

• xorg: xwayland: X.Org X server: Denial of Service via integer underflow in XKB compatibility map handling (CVE-2026-33999)

• xorg: xwayland: X.Org X server: Use-after-free vulnerability leads to server crash and potential memory corruption (CVE-2026-34001)

• xorg: xwayland: X.Org X server: Information exposure and denial of service via out-of-bounds memory access (CVE-2026-34003)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.