Amazon Linux 2023 Security Advisory: ALAS2023-2026-1789
Advisory Released Date: 2026-06-08
Advisory Updated Date: 2026-06-12
FAQs regarding Amazon Linux ALAS/CVE Severity
A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. A mismatch between the X server and the libXfont2 library's maximum font name length can cause a stack buffer overflow during font alias resolution. The server allocates a 256 byte stack buffer but libXfont2's alias target name length is 1024 bytes. A font alias name between 257 and 1023 bytes causes the X server to copy that name into the undersized stack buffer without further checks. This may be used to crash the server, or for privilege escalation if the X server runs as root. (CVE-2026-50256)
A use-after-free flaw was found in the X.Org X server and Xwayland in miSyncDestroyFence(). A client that sets up multiple fence triggers can trigger a use-after-free function pointer call. An attacker would connect to the X server to set up a fence and await that fence, then a second X connection destroys the fence, causing the use-after-free. This may be used to crash the server, or for privilege escalation if the X server runs as root. (CVE-2026-50257)
A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. The X server has multiple stack buffers sized XkbMaxShiftLevel * XkbNumKbdGroups but CheckKeyTypes() does not verify or clamp non-canonical key types to XkbMaxShiftLevel. A client can change key types to excessive shift levels and trigger stack overflows. This is caused by an incomplete fix of CVE-2025-26597. This may be used to crash the server, or for privilege escalation if the X server runs as root. (CVE-2026-50258)
A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. _XkbSetMapChecks() declares a fixed-size stack buffer mapWidths[256] indexed by key type index. The helper function CheckKeyTypes() writes to this buffer at a client-controlled offset, allowing a stack buffer overflow. This may be used to crash the server, or for privilege escalation if the X server runs as root. (CVE-2026-50259)
A use-after-free flaw was found in the X.Org X server and Xwayland in FreeCounter(). A client that sets up multiple SyncCounters and awaits on those triggers can trigger a use-after-free when destroying those counters via a second client connection. This may be used to crash the server, or for privilege escalation if the X server runs as root. (CVE-2026-50260)
A use-after-free flaw was found in the X.Org X server and Xwayland in SyncChangeCounter(). A client that sets up multiple SyncCounters can trigger a use-after-free when destroying those counters via a second client connection while changing those counters. This may be used to crash the server, or for privilege escalation if the X server runs as root. (CVE-2026-50261)
Multiple issues have been found in the X server and Xwayland implementations published by X.Org for which we are releasing security fixes for in xorg-server-21.1.23 and xwayland-24.1.12. (CVE-2026-50262)
A use-after-free flaw was found in the X.Org X server and Xwayland in CreateSaverWindow(). A client can trigger a use-after-free read after changing window attributes and forcing the screen saver, leading to information disclosure. (CVE-2026-50263)
Affected Packages:
xorg-x11-server-Xwayland
Issue Correction:
Run dnf update xorg-x11-server-Xwayland --releasever 2023.12.20260608 or dnf update --advisory ALAS2023-2026-1789 --releasever 2023.12.20260608 to update your system.
More information on how to update your system can be found on this page: Amazon Linux 2023 documentation
aarch64:
xorg-x11-server-Xwayland-debuginfo-24.1.3-1.amzn2023.0.5.aarch64
xorg-x11-server-Xwayland-devel-24.1.3-1.amzn2023.0.5.aarch64
xorg-x11-server-Xwayland-24.1.3-1.amzn2023.0.5.aarch64
xorg-x11-server-Xwayland-debugsource-24.1.3-1.amzn2023.0.5.aarch64
src:
xorg-x11-server-Xwayland-24.1.3-1.amzn2023.0.5.src
x86_64:
xorg-x11-server-Xwayland-debuginfo-24.1.3-1.amzn2023.0.5.x86_64
xorg-x11-server-Xwayland-devel-24.1.3-1.amzn2023.0.5.x86_64
xorg-x11-server-Xwayland-24.1.3-1.amzn2023.0.5.x86_64
xorg-x11-server-Xwayland-debugsource-24.1.3-1.amzn2023.0.5.x86_64
2026-06-12: CVE-2026-50257 was added to this advisory.
2026-06-12: CVE-2026-50260 was added to this advisory.
2026-06-09: CVE-2026-50261 was added to this advisory.
2026-06-09: CVE-2026-50258 was added to this advisory.
2026-06-09: CVE-2026-50263 was added to this advisory.
2026-06-09: CVE-2026-50262 was added to this advisory.
2026-06-09: CVE-2026-50256 was added to this advisory.
2026-06-09: CVE-2026-50259 was added to this advisory.