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CVE-2026-50257— Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: use-after-free in misyncdestroyfence()

Quick assessment

Affected
Red Hat Red Hat Enterprise Linux 10
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

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miSyncDestroyFence中存在释放后重用,可能导致服务器崩溃或权限提升。

CVSS 7.8 · High EPSS 0.20% · P9

Affected Version Matrix 37

VendorProduct Version RangeStatus
Red Hat Red Hat Enterprise Linux 10 0:24.1.9-4.el10_2.2< * unaffected
Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support 0:24.1.5-6.el10_0.1< * unaffected
Red Hat Red Hat Enterprise Linux 6 any unknown
Red Hat Red Hat Enterprise Linux 6 Extended Lifecycle Support - EXTENSION 0:1.1.0-25.el6_10.18< * unaffected
Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support 0:1.20.4-35.el7_9< * unaffected
0:1.8.0-36.el7_9.5< * unaffected
Red Hat Red Hat Enterprise Linux 8 0:21.1.3-20.el8_10.2< * unaffected
0:1.20.11-28.el8_10.2< * unaffected
0:1.15.0-10.el8_10< * unaffected
Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support 0:1.20.10-5.el8_4< * unaffected
0:1.11.0-8.el8_4.16< * unaffected
Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On 0:1.20.10-5.el8_4< * unaffected
0:1.11.0-8.el8_4.16< * unaffected
Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support 0:1.20.11-8.el8_6< * unaffected
0:21.1.3-2.el8_6.7< * unaffected
0:1.12.0-6.el8_6.18< * unaffected
Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On 0:1.20.11-8.el8_6< * unaffected
0:21.1.3-2.el8_6.7< * unaffected
0:1.12.0-6.el8_6.18< * unaffected
Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service 0:1.20.11-19.el8_8< * unaffected
0:21.1.3-13.el8_8.1< * unaffected
0:1.12.0-15.el8_8.18< * unaffected
Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions 0:1.20.11-19.el8_8< * unaffected
0:21.1.3-13.el8_8.1< * unaffected
0:1.12.0-15.el8_8.18< * unaffected
Red Hat Red Hat Enterprise Linux 9 0:24.1.9-4.el9_8.2< * unaffected
0:1.20.11-34.el9_8.2< * unaffected
0:1.15.0-7.el9_8.2< * unaffected
Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 0:1.20.11-21.el9_2< * unaffected
0:21.1.3-10.el9_2.1< * unaffected
0:1.12.0-14.el9_2.15< * unaffected
Red Hat Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions 0:1.20.11-29.el9_4< * unaffected
0:22.1.9-8.el9_4.1< * unaffected
0:1.13.1-8.el9_4.10< * unaffected
Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support 0:1.20.11-34.el9_6< * unaffected
0:23.2.7-6.el9_6.1< * unaffected
0:1.14.1-11.el9_6< * unaffected
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I. Basic Information for CVE-2026-50257

Vulnerability Information

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Vulnerability Title
Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: use-after-free in misyncdestroyfence()
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
释放后使用
Source: CVE Program / CVE List V5
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miSyncDestroyFence中存在释放后重用,可能导致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

Vendor Product Affected Versions CPE Subscribe
Red Hat Red Hat Enterprise Linux 10 0:24.1.9-4.el10_2.2 ~ * cpe:/o:redhat:enterprise_linux:10.2
Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support 0:24.1.5-6.el10_0.1 ~ * cpe:/o:redhat:enterprise_linux_eus:10.0
Red Hat Red Hat Enterprise Linux 6 Extended Lifecycle Support - EXTENSION 0:1.1.0-25.el6_10.18 ~ * cpe:/o:redhat:rhel_els:6
Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support 0:1.20.4-35.el7_9 ~ * cpe:/o:redhat:rhel_els:7
Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support 0:1.8.0-36.el7_9.5 ~ * cpe:/o:redhat:rhel_els:7
Red Hat Red Hat Enterprise Linux 8 0:21.1.3-20.el8_10.2 ~ * cpe:/a:redhat:enterprise_linux:8::appstream
Red Hat Red Hat Enterprise Linux 8 0:1.20.11-28.el8_10.2 ~ * cpe:/a:redhat:enterprise_linux:8::appstream
Red Hat Red Hat Enterprise Linux 8 0:1.15.0-10.el8_10 ~ * cpe:/a:redhat:enterprise_linux:8::appstream
Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support 0:1.20.10-5.el8_4 ~ * cpe:/a:redhat:rhel_aus:8.4::appstream
Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support 0:1.11.0-8.el8_4.16 ~ * cpe:/a:redhat:rhel_aus:8.4::appstream
Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On 0:1.20.10-5.el8_4 ~ * cpe:/a:redhat:rhel_aus:8.4::appstream
Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On 0:1.11.0-8.el8_4.16 ~ * cpe:/a:redhat:rhel_aus:8.4::appstream
Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support 0:1.20.11-8.el8_6 ~ * cpe:/a:redhat:rhel_aus:8.6::appstream
Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support 0:21.1.3-2.el8_6.7 ~ * cpe:/a:redhat:rhel_aus:8.6::appstream
Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support 0:1.12.0-6.el8_6.18 ~ * cpe:/a:redhat:rhel_aus:8.6::appstream
Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On 0:1.20.11-8.el8_6 ~ * cpe:/a:redhat:rhel_aus:8.6::appstream
Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On 0:21.1.3-2.el8_6.7 ~ * cpe:/a:redhat:rhel_aus:8.6::appstream
Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On 0:1.12.0-6.el8_6.18 ~ * cpe:/a:redhat:rhel_aus:8.6::appstream
Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service 0:1.20.11-19.el8_8 ~ * cpe:/a:redhat:rhel_e4s:8.8::appstream
Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service 0:21.1.3-13.el8_8.1 ~ * cpe:/a:redhat:rhel_e4s:8.8::appstream
Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service 0:1.12.0-15.el8_8.18 ~ * cpe:/a:redhat:rhel_e4s:8.8::appstream
Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions 0:1.20.11-19.el8_8 ~ * cpe:/a:redhat:rhel_e4s:8.8::appstream
Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions 0:21.1.3-13.el8_8.1 ~ * cpe:/a:redhat:rhel_e4s:8.8::appstream
Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions 0:1.12.0-15.el8_8.18 ~ * cpe:/a:redhat:rhel_e4s:8.8::appstream
Red Hat Red Hat Enterprise Linux 9 0:24.1.9-4.el9_8.2 ~ * cpe:/a:redhat:enterprise_linux:9::appstream
Red Hat Red Hat Enterprise Linux 9 0:1.20.11-34.el9_8.2 ~ * cpe:/a:redhat:enterprise_linux:9::appstream
Red Hat Red Hat Enterprise Linux 9 0:1.15.0-7.el9_8.2 ~ * cpe:/a:redhat:enterprise_linux:9::appstream
Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 0:1.20.11-21.el9_2 ~ * cpe:/a:redhat:rhel_e4s:9.2::appstream
Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 0:21.1.3-10.el9_2.1 ~ * cpe:/a:redhat:rhel_e4s:9.2::appstream
Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 0:1.12.0-14.el9_2.15 ~ * cpe:/a:redhat:rhel_e4s:9.2::appstream

II. Public POCs for CVE-2026-50257

# POC Description Source Link Shenlong Link
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III. Intelligence Information for CVE-2026-50257

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Patches & Fixes for CVE-2026-50257 (1)

Vendor Advisories for CVE-2026-50257 (26)

Mailing List Discussions for CVE-2026-50257 (1)

Other References for CVE-2026-50257 (4)

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

CVE-2026-11332 7.8 HIGH Ansible-core: argument injection in ansible-galaxy role install leads to arbitrary code ex
CVE-2026-50256 7.8 HIGH Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: stack buffer overflow in font
CVE-2026-50259 7.8 HIGH Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: stack buffer overflow in xkb s
CVE-2026-50258 7.8 HIGH Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: stack buffer overflow in xkb k
CVE-2026-50260 7.8 HIGH Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: use-after-free in freecounter(
CVE-2026-50261 7.8 HIGH Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: use-after-free in syncchangeco
CVE-2026-50264 7.8 HIGH Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: out-of-bounds heap write in dr
CVE-2026-50262 5.5 MEDIUM Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: out-of-bounds read/write in gl
CVE-2026-50263 5.5 MEDIUM Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: use-after-free information dis
CVE-2026-9088 2.7 LOW Keycloak: keycloak: information disclosure due to user profile permission bypass

IV. Related Vulnerabilities

V. Comments for CVE-2026-50257

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