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CVE-2026-50261— Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: use-after-free in syncchangecounter()

CVSS 7.8 · High EPSS 0.14% · P3

Affected Version Matrix 11

VendorProductVersion RangeStatus
Red HatRed Hat Enterprise Linux 10anyaffected
Red HatRed Hat Enterprise Linux 6anyaffected
anyunknown
Red HatRed Hat Enterprise Linux 7anyaffected
anyaffected
Red HatRed Hat Enterprise Linux 80:21.1.3-20.el8_10.2< *unaffected
0:1.20.11-28.el8_10.2< *unaffected
anyaffected
Red HatRed Hat Enterprise Linux 90:24.1.9-4.el9_8.2< *unaffected
0:1.20.11-34.el9_8.2< *unaffected
anyaffected
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I. Basic Information for CVE-2026-50261

Vulnerability Information
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Vulnerability Title
Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: use-after-free in syncchangecounter()
Source: NVD (National Vulnerability Database)
Vulnerability Description
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.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: NVD (National Vulnerability Database)
Vulnerability Type
释放后使用
Source: NVD (National Vulnerability Database)
Vulnerability Title
X.Org X server和Xwayland 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
X.Org X Server是X.Org基金会的一款X Window系统显示服务器。Xwayland是Xwayland开源的一个通信协议，规定了显示服务器与其客户机之间的通信方式。 X.Org X server和Xwayland存在资源管理错误漏洞，该漏洞源于SyncChangeCounter()中的释放后重用问题，可能导致客户端在更改计数器时通过第二个客户端连接销毁计数器触发释放后重用，造成服务器崩溃或权限提升。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

VendorProductAffected VersionsCPESubscribe
Red HatRed Hat Enterprise Linux 10 0:24.1.9-4.el10_2.2 ~ * cpe:/o:redhat:enterprise_linux:10.2
Red HatRed Hat Enterprise Linux 8 0:21.1.3-20.el8_10.2 ~ * cpe:/a:redhat:enterprise_linux:8::appstream
Red HatRed Hat Enterprise Linux 8 0:1.20.11-28.el8_10.2 ~ * cpe:/a:redhat:enterprise_linux:8::appstream
Red HatRed Hat Enterprise Linux 8 0:1.15.0-10.el8_10 ~ * cpe:/a:redhat:enterprise_linux:8::appstream
Red HatRed Hat Enterprise Linux 9 0:24.1.9-4.el9_8.2 ~ * cpe:/a:redhat:enterprise_linux:9::appstream
Red HatRed Hat Enterprise Linux 9 0:1.20.11-34.el9_8.2 ~ * cpe:/a:redhat:enterprise_linux:9::appstream
Red HatRed Hat Enterprise Linux 9 0:1.15.0-7.el9_8.2 ~ * cpe:/a:redhat:enterprise_linux:9::appstream
Red HatRed Hat Enterprise Linux 6-cpe:/o:redhat:enterprise_linux:6
Red HatRed Hat Enterprise Linux 6-cpe:/o:redhat:enterprise_linux:6
Red HatRed Hat Enterprise Linux 7-cpe:/o:redhat:enterprise_linux:7
Red HatRed Hat Enterprise Linux 7-cpe:/o:redhat:enterprise_linux:7

II. Public POCs for CVE-2026-50261

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III. Intelligence Information for CVE-2026-50261

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Patches & Fixes for CVE-2026-50261 (1)

Vendor Advisories for CVE-2026-50261 (3)

Mailing List Discussions for CVE-2026-50261 (1)

Other References for CVE-2026-50261 (6)

Same Patch Batch · Red Hat · 2026-06-05 · 11 CVEs total

CVE-2026-113327.8 HIGHAnsible-core: argument injection in ansible-galaxy role install leads to arbitrary code ex
CVE-2026-502567.8 HIGHXorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: stack buffer overflow in font
CVE-2026-502577.8 HIGHXorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: use-after-free in misyncdestro
CVE-2026-502597.8 HIGHXorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: stack buffer overflow in xkb s
CVE-2026-502587.8 HIGHXorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: stack buffer overflow in xkb k
CVE-2026-502607.8 HIGHXorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: use-after-free in freecounter(
CVE-2026-502647.8 HIGHXorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: out-of-bounds heap write in dr
CVE-2026-502625.5 MEDIUMXorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: out-of-bounds read/write in gl
CVE-2026-502635.5 MEDIUMXorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: use-after-free information dis
CVE-2026-90882.7 LOWKeycloak: keycloak: information disclosure due to user profile permission bypass

IV. Related Vulnerabilities

Same product: Red Hat Enterprise Linux 10
Same vendor: Red Hat
Same weakness: CWE-416

V. Comments for CVE-2026-50261

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