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AlmaLinux 9 : xorg-x11-server-Xwayland (ALSA-2026:26590)

high Nessus Plugin ID 324820

Synopsis

The remote AlmaLinux host is missing one or more security updates.

Description

The remote AlmaLinux 9 host has packages installed that are affected by multiple vulnerabilities as referenced in the ALSA-2026:26590 advisory.

 * xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: stack buffer overflow in font alias resolution due to libXfont2 name length mismatch (CVE-2026-50256)
 * xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: use-after-free in miSyncDestroyFence() (CVE-2026-50257)
 * xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: stack buffer overflow in XKB key types due to unchecked shift levels (CVE-2026-50258)
 * xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: stack buffer overflow in XKB SetMap request via mapWidths indexing (CVE-2026-50259)
 * xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: use-after-free in FreeCounter() (CVE-2026-50260)
 * xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: use-after-free in SyncChangeCounter() (CVE-2026-50261)
 * xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: out-of-bounds read/write in GLX ChangeDrawableAttributes (CVE-2026-50262)
 * xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: use-after-free information disclosure in CreateSaverWindow() (CVE-2026-50263)
 * xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: out-of-bounds heap write in DRI2 DRIGetBuffers/DRIGetBuffersWithFormat (CVE-2026-50264)


 Bug Fix(es) and Enhancement(s):

 * [xwayland] Backport other security fixes without a CVE assigned [almalinux-9.8.z] (JIRA:AlmaLinux-184292)

Tenable has extracted the preceding description block directly from the AlmaLinux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Update the affected xorg-x11-server-Xwayland and / or xorg-x11-server-Xwayland-devel packages.

See Also

https://access.redhat.com/errata/RHSA-2026:26590

https://errata.almalinux.org/9/ALSA-2026-26590.html

Plugin Details

Severity: High

ID: 324820

File Name: alma_linux_ALSA-2026-26590.nasl

Version: 1.1

Type: Local

Published: 7/2/2026

Updated: 7/2/2026

Supported Sensors: Nessus Agent, Continuous Assessment, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.9

Percentile: 57.98

CVSS v2

Risk Factor: Medium

Base Score: 6.8

Temporal Score: 5

Vector: CVSS2#AV:L/AC:L/Au:S/C:C/I:C/A:C

CVSS Score Source: CVE-2026-50264

CVSS v3

Risk Factor: High

Base Score: 7.8

Temporal Score: 6.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:alma:linux:9::highavailability, cpe:/o:alma:linux:9::resilientstorage, cpe:/o:alma:linux:9::appstream, cpe:/o:alma:linux:9::realtime, p-cpe:/a:alma:linux:xorg-x11-server-xwayland, cpe:/o:alma:linux:9, cpe:/o:alma:linux:9::sap_hana, cpe:/o:alma:linux:9::supplementary, p-cpe:/a:alma:linux:xorg-x11-server-xwayland-devel, cpe:/o:alma:linux:9::sap, cpe:/o:alma:linux:9::crb, cpe:/o:alma:linux:9::nfv, cpe:/o:alma:linux:9::baseos

Required KB Items: Host/local_checks_enabled, Host/cpu, Host/AlmaLinux/release, Host/AlmaLinux/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 6/17/2026

Vulnerability Publication Date: 6/1/2026

Reference Information

CVE: CVE-2026-50256, CVE-2026-50257, CVE-2026-50258, CVE-2026-50259, CVE-2026-50260, CVE-2026-50261, CVE-2026-50262, CVE-2026-50263, CVE-2026-50264

CWE: 121, 125, 416, 787

RHSA: 2026:26590