CVE-2025-26601

A use-after-free flaw was found in X.Org and Xwayland. When changing an alarm, the values of the change mask are evaluated one after the other, changing the trigger values as requested, and eventually, SyncInitTrigger() is called. If one of the changes triggers an error, the function will return early, not adding the new sync object, possibly causing a use-after-free when the alarm eventually triggers.

A use-after-free flaw was found in X.Org and Xwayland. When changing an alarm, the values of the change mask are evaluated one after the other, changing the trigger values as requested, and eventually, SyncInitTrigger() is called. If one of the changes triggers an error, the function will return early, not adding the new sync object, possibly causing a use-after-free when the alarm eventually triggers.

A use-after-free flaw was found in X.Org and Xwayland. When changing an alarm, the values of the change mask are evaluated one after the other, changing the trigger values as requested, and eventually, SyncInitTrigger() is called. If one of the changes triggers an error, the function will return early, not adding the new sync object, possibly causing a use-after-free when the alarm eventually triggers.

A use-after-free flaw was found in X.Org and Xwayland. When changing an alarm, the values of the change mask are evaluated one after the other, changing the trigger values as requested, and eventually, SyncInitTrigger() is called. If one of the changes triggers an error, the function will return early, not adding the new sync object, possibly causing a use-after-free when the alarm eventually triggers.

X.Org X11 X server

Security Fix(es):

A use-after-free flaw was found in X.Org and Xwayland. The root cursor is referenced in the X server as a global variable. If a client frees the root cursor, the internal reference points to freed memory and causes a use-after-free.(CVE-2025-26594)

A buffer overflow flaw was found in X.Org and Xwayland. The code in XkbVModMaskText() allocates a fixed-sized buffer on the stack and copies the names of the virtual modifiers to that buffer. The code fails to check the bounds of the buffer and would copy the data regardless of the size.(CVE-2025-26595)

A heap overflow flaw was found in X.Org and Xwayland. The computation of the length in XkbSizeKeySyms() differs from what is written in XkbWriteKeySyms(), which may lead to a heap-based buffer overflow.(CVE-2025-26596)

A buffer overflow flaw was found in X.Org and Xwayland. If XkbChangeTypesOfKey() is called with a 0 group, it will resize the key symbols table to 0 but leave the key actions unchanged. If the same function is later called with a non-zero value of groups, this will cause a buffer overflow because the key actions are of the wrong size.(CVE-2025-26597)

An out-of-bounds write flaw was found in X.Org and Xwayland. The function GetBarrierDevice() searches for the pointer device based on its device ID and returns the matching value, or supposedly NULL, if no match was found. However, the code will return the last element of the list if no matching device ID is found, which can lead to out-of-bounds memory access.(CVE-2025-26598)

An access to an uninitialized pointer flaw was found in X.Org and Xwayland. The function compCheckRedirect() may fail if it cannot allocate the backing pixmap. In that case, compRedirectWindow() will return a BadAlloc error without validating the window tree marked just before, which leaves the validated data partly initialized and the use of an uninitialized pointer later.(CVE-2025-26599)

A use-after-free flaw was found in X.Org and Xwayland. When a device is removed while still frozen, the events queued for that device remain while the device is freed. Replaying the events will cause a use-after-free.(CVE-2025-26600)

A use-after-free flaw was found in X.Org and Xwayland. When changing an alarm, the values of the change mask are evaluated one after the other, changing the trigger values as requested, and eventually, SyncInitTrigger() is called. If one of the changes triggers an error, the function will return early, not adding the new sync object, possibly causing a use-after-free when the alarm eventually triggers.(CVE-2025-26601)

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):

• X.Org: Xwayland: Use-after-free of the root cursor (CVE-2025-26594)

• xorg: xwayland: Use-after-free in SyncInitTrigger() (CVE-2025-26601)

• xorg: xwayland: Use-after-free in PlayReleasedEvents() (CVE-2025-26600)

• xorg: xwayland: Use of uninitialized pointer in compRedirectWindow() (CVE-2025-26599)

• xorg: xwayland: Out-of-bounds write in CreatePointerBarrierClient() (CVE-2025-26598)

• xorg: xwayland: Buffer overflow in XkbChangeTypesOfKey() (CVE-2025-26597)

• xorg: xwayland: Heap overflow in XkbWriteKeySyms() (CVE-2025-26596)

• Xorg: xwayland: Buffer overflow in XkbVModMaskText() (CVE-2025-26595)

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):

• X.Org: Xwayland: Use-after-free of the root cursor (CVE-2025-26594)

• xorg: xwayland: Use-after-free in SyncInitTrigger() (CVE-2025-26601)

• xorg: xwayland: Use-after-free in PlayReleasedEvents() (CVE-2025-26600)

• xorg: xwayland: Use of uninitialized pointer in compRedirectWindow() (CVE-2025-26599)

• xorg: xwayland: Out-of-bounds write in CreatePointerBarrierClient() (CVE-2025-26598)

• xorg: xwayland: Buffer overflow in XkbChangeTypesOfKey() (CVE-2025-26597)

• xorg: xwayland: Heap overflow in XkbWriteKeySyms() (CVE-2025-26596)

• Xorg: xwayland: Buffer overflow in XkbVModMaskText() (CVE-2025-26595)

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-x11-server: tigervnc: heap-based buffer overflow privilege escalation vulnerability (CVE-2024-9632)

• X.Org: Xwayland: Use-after-free of the root cursor (CVE-2025-26594)

• xorg: xwayland: Use-after-free in SyncInitTrigger() (CVE-2025-26601)

• xorg: xwayland: Use-after-free in PlayReleasedEvents() (CVE-2025-26600)

• xorg: xwayland: Use of uninitialized pointer in compRedirectWindow() (CVE-2025-26599)

• xorg: xwayland: Out-of-bounds write in CreatePointerBarrierClient() (CVE-2025-26598)

• xorg: xwayland: Buffer overflow in XkbChangeTypesOfKey() (CVE-2025-26597)

• xorg: xwayland: Heap overflow in XkbWriteKeySyms() (CVE-2025-26596)

• Xorg: xwayland: Buffer overflow in XkbVModMaskText() (CVE-2025-26595)

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.

Additional Changes:

For detailed information on changes in this release, see the Rocky Linux 9 Release Notes linked from the References section.

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

Security Fix(es):

• xorg-x11-server: tigervnc: heap-based buffer overflow privilege escalation vulnerability (CVE-2024-9632)

• X.Org: Xwayland: Use-after-free of the root cursor (CVE-2025-26594)

• xorg: xwayland: Use-after-free in SyncInitTrigger() (CVE-2025-26601)

• xorg: xwayland: Use-after-free in PlayReleasedEvents() (CVE-2025-26600)

• xorg: xwayland: Use of uninitialized pointer in compRedirectWindow() (CVE-2025-26599)

• xorg: xwayland: Out-of-bounds write in CreatePointerBarrierClient() (CVE-2025-26598)

• xorg: xwayland: Buffer overflow in XkbChangeTypesOfKey() (CVE-2025-26597)

• xorg: xwayland: Heap overflow in XkbWriteKeySyms() (CVE-2025-26596)

• Xorg: xwayland: Buffer overflow in XkbVModMaskText() (CVE-2025-26595)

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.

Additional Changes:

For detailed information on changes in this release, see the Rocky Linux 9 Release Notes linked from the References section.

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

Security Fix(es):

• xorg-x11-server: tigervnc: heap-based buffer overflow privilege escalation vulnerability (CVE-2024-9632)

• X.Org: Xwayland: Use-after-free of the root cursor (CVE-2025-26594)

• xorg: xwayland: Use-after-free in SyncInitTrigger() (CVE-2025-26601)

• xorg: xwayland: Use-after-free in PlayReleasedEvents() (CVE-2025-26600)

• xorg: xwayland: Use of uninitialized pointer in compRedirectWindow() (CVE-2025-26599)

• xorg: xwayland: Out-of-bounds write in CreatePointerBarrierClient() (CVE-2025-26598)

• xorg: xwayland: Buffer overflow in XkbChangeTypesOfKey() (CVE-2025-26597)

• xorg: xwayland: Heap overflow in XkbWriteKeySyms() (CVE-2025-26596)

• Xorg: xwayland: Buffer overflow in XkbVModMaskText() (CVE-2025-26595)

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.

A use-after-free flaw was found in X.Org and Xwayland. When changing an alarm, the values of the change mask are evaluated one after the other, changing the trigger values as requested, and eventually, SyncInitTrigger() is called. If one of the changes triggers an error, the function will return early, not adding the new sync object, possibly causing a use-after-free when the alarm eventually triggers.

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):

• X.Org: Xwayland: Use-after-free of the root cursor (CVE-2025-26594)
• xorg: xwayland: Use-after-free in SyncInitTrigger() (CVE-2025-26601)
• xorg: xwayland: Use-after-free in PlayReleasedEvents() (CVE-2025-26600)
• xorg: xwayland: Use of uninitialized pointer in compRedirectWindow() (CVE-2025-26599)
• xorg: xwayland: Out-of-bounds write in CreatePointerBarrierClient() (CVE-2025-26598)
• xorg: xwayland: Buffer overflow in XkbChangeTypesOfKey() (CVE-2025-26597)
• xorg: xwayland: Heap overflow in XkbWriteKeySyms() (CVE-2025-26596)
• Xorg: xwayland: Buffer overflow in XkbVModMaskText() (CVE-2025-26595)

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):

• X.Org: Xwayland: Use-after-free of the root cursor (CVE-2025-26594)
• xorg: xwayland: Use-after-free in SyncInitTrigger() (CVE-2025-26601)
• xorg: xwayland: Use-after-free in PlayReleasedEvents() (CVE-2025-26600)
• xorg: xwayland: Use of uninitialized pointer in compRedirectWindow() (CVE-2025-26599)
• xorg: xwayland: Out-of-bounds write in CreatePointerBarrierClient() (CVE-2025-26598)
• xorg: xwayland: Buffer overflow in XkbChangeTypesOfKey() (CVE-2025-26597)
• xorg: xwayland: Heap overflow in XkbWriteKeySyms() (CVE-2025-26596)
• Xorg: xwayland: Buffer overflow in XkbVModMaskText() (CVE-2025-26595)

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-x11-server: tigervnc: heap-based buffer overflow privilege escalation vulnerability (CVE-2024-9632)
• X.Org: Xwayland: Use-after-free of the root cursor (CVE-2025-26594)
• xorg: xwayland: Use-after-free in SyncInitTrigger() (CVE-2025-26601)
• xorg: xwayland: Use-after-free in PlayReleasedEvents() (CVE-2025-26600)
• xorg: xwayland: Use of uninitialized pointer in compRedirectWindow() (CVE-2025-26599)
• xorg: xwayland: Out-of-bounds write in CreatePointerBarrierClient() (CVE-2025-26598)
• xorg: xwayland: Buffer overflow in XkbChangeTypesOfKey() (CVE-2025-26597)
• xorg: xwayland: Heap overflow in XkbWriteKeySyms() (CVE-2025-26596)
• Xorg: xwayland: Buffer overflow in XkbVModMaskText() (CVE-2025-26595)

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.

Additional Changes:

For detailed information on changes in this release, see the AlmaLinuxRelease Notes linked from the References section.

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

Security Fix(es):

• xorg-x11-server: tigervnc: heap-based buffer overflow privilege escalation vulnerability (CVE-2024-9632)
• X.Org: Xwayland: Use-after-free of the root cursor (CVE-2025-26594)
• xorg: xwayland: Use-after-free in SyncInitTrigger() (CVE-2025-26601)
• xorg: xwayland: Use-after-free in PlayReleasedEvents() (CVE-2025-26600)
• xorg: xwayland: Use of uninitialized pointer in compRedirectWindow() (CVE-2025-26599)
• xorg: xwayland: Out-of-bounds write in CreatePointerBarrierClient() (CVE-2025-26598)
• xorg: xwayland: Buffer overflow in XkbChangeTypesOfKey() (CVE-2025-26597)
• xorg: xwayland: Heap overflow in XkbWriteKeySyms() (CVE-2025-26596)
• Xorg: xwayland: Buffer overflow in XkbVModMaskText() (CVE-2025-26595)

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.

Additional Changes:

For detailed information on changes in this release, see the AlmaLinuxRelease Notes linked from the References section.

• CVE-2025-26601: xorg-x11-server: fix use-after-free issue by adding check to ensure new sync object is added before alarm triggers

• CVE-2025-26594: refuse to free the root cursor and keep its ref
• CVE-2025-26595: fix buffer overflow in XkbVModMaskText()
• CVE-2025-26596: xkb: fix computation of XkbSizeKeySyms
• CVE-2025-26597: xkb: fix buffer overflow in XkbChangeTypesOfKey()
• CVE-2025-26598: Xi: Fix barrier device search
• CVE-2025-26599: always initialize the border clip in compAllocPixmap()
• CVE-2025-26600: dix: Dequeue pending events on frozen device on removal
• CVE-2025-26601: postpone actual changes in SyncChangeAlarmAttributes()

• CVE-2025-26594: refuse to free the root cursor and keep its ref
• CVE-2025-26595: fix buffer overflow in XkbVModMaskText()
• CVE-2025-26596: xkb: fix computation of XkbSizeKeySyms
• CVE-2025-26597: xkb: fix buffer overflow in XkbChangeTypesOfKey()
• CVE-2025-26598: Xi: Fix barrier device search
• CVE-2025-26599: always initialize the border clip in compAllocPixmap()
• CVE-2025-26600: dix: Dequeue pending events on frozen device on removal
• CVE-2025-26601: postpone actual changes in SyncChangeAlarmAttributes()

• Rebuilt with xorg-x11-server-1.20.4-99.el7_9.tuxcare.els7, mitigating the security vulnerabilities identified by the following CVEs: CVE-2025-26594, CVE-2025-26595, CVE-2025-26596, CVE-2025-26597 CVE-2025-26598, CVE-2025-26599, CVE-2025-26600 and CVE-2025-26601, CVE-2025-49175, CVE-2025-49176, CVE-2025-49178, CVE-2025-49179, CVE-2025-49180

Use-after-free of the root cursor. (CVE-2025-26594) Buffer overflow in XkbVModMaskText(). (CVE-2025-26595) Heap overflow in XkbWriteKeySyms(). (CVE-2025-26596) Buffer overflow in XkbChangeTypesOfKey(). (CVE-2025-26597) Out-of-bounds write in CreatePointerBarrierClient(). (CVE-2025-26598) Use of uninitialized pointer in compRedirectWindow(). (CVE-2025-26599) Use-after-free in PlayReleasedEvents(). (CVE-2025-26600) Use-after-free in SyncInitTrigger(). (CVE-2025-26601)

These are all security issues fixed in the xorg-x11-server-21.1.15-2.1 package on the GA media of openSUSE Tumbleweed.

These are all security issues fixed in the xwayland-24.1.5-2.1 package on the GA media of openSUSE Tumbleweed.

This update for xwayland fixes the following issues:

• CVE-2025-26594: Use-after-free of the root cursor (bsc#1237427).
• CVE-2025-26595: Buffer overflow in XkbVModMaskText() (bsc#1237429).
• CVE-2025-26596: Heap overflow in XkbWriteKeySyms() (bsc#1237430).
• CVE-2025-26597: Buffer overflow in XkbChangeTypesOfKey() (bsc#1237431).
• CVE-2025-26598: Out-of-bounds write in CreatePointerBarrierClient() (bsc#1237432).
• CVE-2025-26599: Use of uninitialized pointer in compRedirectWindow() (bsc#1237433).
• CVE-2025-26600: Use-after-free in PlayReleasedEvents() (bsc#1237434).
• CVE-2025-26601: Use-after-free in SyncInitTrigger() (bsc#1237435).

This update for xorg-x11-server fixes the following issues:

• CVE-2025-26594: Use-after-free of the root cursor (bsc#1237427).
• CVE-2025-26595: Buffer overflow in XkbVModMaskText() (bsc#1237429).
• CVE-2025-26596: Heap overflow in XkbWriteKeySyms() (bsc#1237430).
• CVE-2025-26597: Buffer overflow in XkbChangeTypesOfKey() (bsc#1237431).
• CVE-2025-26598: Out-of-bounds write in CreatePointerBarrierClient() (bsc#1237432).
• CVE-2025-26599: Use of uninitialized pointer in compRedirectWindow() (bsc#1237433).
• CVE-2025-26600: Use-after-free in PlayReleasedEvents() (bsc#1237434).
• CVE-2025-26601: Use-after-free in SyncInitTrigger() (bsc#1237435).

This update for xorg-x11-server fixes the following issues:

• CVE-2025-26594: Use-after-free of the root cursor (bsc#1237427).
• CVE-2025-26595: Buffer overflow in XkbVModMaskText() (bsc#1237429).
• CVE-2025-26596: Heap overflow in XkbWriteKeySyms() (bsc#1237430).
• CVE-2025-26597: Buffer overflow in XkbChangeTypesOfKey() (bsc#1237431).
• CVE-2025-26598: Out-of-bounds write in CreatePointerBarrierClient() (bsc#1237432).
• CVE-2025-26599: Use of uninitialized pointer in compRedirectWindow() (bsc#1237433).
• CVE-2025-26600: Use-after-free in PlayReleasedEvents() (bsc#1237434).
• CVE-2025-26601: Use-after-free in SyncInitTrigger() (bsc#1237435).

This update for xorg-x11-server fixes the following issues:

• CVE-2025-26594: Use-after-free of the root cursor (bsc#1237427).
• CVE-2025-26595: Buffer overflow in XkbVModMaskText() (bsc#1237429).
• CVE-2025-26596: Heap overflow in XkbWriteKeySyms() (bsc#1237430).
• CVE-2025-26597: Buffer overflow in XkbChangeTypesOfKey() (bsc#1237431).
• CVE-2025-26598: Out-of-bounds write in CreatePointerBarrierClient() (bsc#1237432).
• CVE-2025-26599: Use of uninitialized pointer in compRedirectWindow() (bsc#1237433).
• CVE-2025-26600: Use-after-free in PlayReleasedEvents() (bsc#1237434).
• CVE-2025-26601: Use-after-free in SyncInitTrigger() (bsc#1237435).

This update for xorg-x11-server fixes the following issues:

• CVE-2025-26594: Use-after-free of the root cursor (bsc#1237427).
• CVE-2025-26595: Buffer overflow in XkbVModMaskText() (bsc#1237429).
• CVE-2025-26596: Heap overflow in XkbWriteKeySyms() (bsc#1237430).
• CVE-2025-26597: Buffer overflow in XkbChangeTypesOfKey() (bsc#1237431).
• CVE-2025-26598: Out-of-bounds write in CreatePointerBarrierClient() (bsc#1237432).
• CVE-2025-26599: Use of uninitialized pointer in compRedirectWindow() (bsc#1237433).
• CVE-2025-26600: Use-after-free in PlayReleasedEvents() (bsc#1237434).
• CVE-2025-26601: Use-after-free in SyncInitTrigger() (bsc#1237435).

This update for xorg-x11-server fixes the following issues:

• CVE-2025-26594: Use-after-free of the root cursor (bsc#1237427).
• CVE-2025-26595: Buffer overflow in XkbVModMaskText() (bsc#1237429).
• CVE-2025-26596: Heap overflow in XkbWriteKeySyms() (bsc#1237430).
• CVE-2025-26597: Buffer overflow in XkbChangeTypesOfKey() (bsc#1237431).
• CVE-2025-26598: Out-of-bounds write in CreatePointerBarrierClient() (bsc#1237432).
• CVE-2025-26599: Use of uninitialized pointer in compRedirectWindow() (bsc#1237433).
• CVE-2025-26600: Use-after-free in PlayReleasedEvents() (bsc#1237434).
• CVE-2025-26601: Use-after-free in SyncInitTrigger() (bsc#1237435).

Jan-Niklas Sohn discovered that the X.Org X Server incorrectly handled certain memory operations. An attacker could use these issues to cause the X Server to crash, leading to a denial of service, or possibly execute arbitrary code.

USN-7299-1 fixed several vulnerabilities in X.Org. This update provides the corresponding update for Ubuntu 16.04 LTS and Ubuntu 18.04 LTS.

Original advisory details:

Jan-Niklas Sohn discovered that the X.Org X Server incorrectly handled certain memory operations. An attacker could use these issues to cause the X Server to crash, leading to a denial of service, or possibly execute arbitrary code.