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CVE Record

CVE-2026-50256: Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: stack buffer overflow in font alias resolution due to libxfont2 name length mismatch

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.

HighCVSS 7.8Not KEV-listedUpdated
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Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CWE-121: Exact CWE lookup

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CVE-2026-50256 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
7Timeline events
2ADP providers
35Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: total

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9redhat
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2026-50256Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. ADP timelineredhat-SADP

    Reported to Red Hat.

  2. Source timelineredhat

    Reported to Red Hat.

  3. ADP timelineredhat-SADP

    Made public.

  4. Source timelineredhat

    Made public.

  5. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  6. CVE publishedCVE Program

    The CVE record was published.

  7. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPxorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: stack buffer overflow in font alias resolution due to libXfont2 name length mismatch
other:Red Hat severity ratingcvssV3_1
  • 2026-05-15T03:14:46.000Z: Reported to Red Hat.
  • 2026-06-02T00:00:00.000Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Red HatRed Hat Enterprise Linux 10xorg-x11-server-Xwayland, 0:24.1.9-4.el10_2.2affected
Red HatRed Hat Enterprise Linux 10.0 Extended Update Supportxorg-x11-server-Xwayland, 0:24.1.5-6.el10_0.1affected
Red HatRed Hat Enterprise Linux 6 Extended Lifecycle Support - EXTENSIONtigervnc, 0:1.1.0-25.el6_10.18affected
Red HatRed Hat Enterprise Linux 7 Extended Lifecycle Supportxorg-x11-server, 0:1.20.4-35.el7_9affected
Red HatRed Hat Enterprise Linux 7 Extended Lifecycle Supporttigervnc, 0:1.8.0-36.el7_9.5affected
Red HatRed Hat Enterprise Linux 8xorg-x11-server-Xwayland, 0:21.1.3-20.el8_10.2affected
Red HatRed Hat Enterprise Linux 8xorg-x11-server, 0:1.20.11-28.el8_10.2affected
Red HatRed Hat Enterprise Linux 8tigervnc, 0:1.15.0-10.el8_10affected
Red HatRed Hat Enterprise Linux 8.4 Advanced Mission Critical Update Supportxorg-x11-server, 0:1.20.10-5.el8_4affected
Red HatRed Hat Enterprise Linux 8.4 Advanced Mission Critical Update Supporttigervnc, 0:1.11.0-8.el8_4.16affected
Red HatRed Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-Onxorg-x11-server, 0:1.20.10-5.el8_4affected
Red HatRed Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-Ontigervnc, 0:1.11.0-8.el8_4.16affected
Red HatRed Hat Enterprise Linux 8.6 Advanced Mission Critical Update Supportxorg-x11-server, 0:1.20.11-8.el8_6affected
Red HatRed Hat Enterprise Linux 8.6 Advanced Mission Critical Update Supportxorg-x11-server-Xwayland, 0:21.1.3-2.el8_6.7affected
Red HatRed Hat Enterprise Linux 8.6 Advanced Mission Critical Update Supporttigervnc, 0:1.12.0-6.el8_6.18affected
Red HatRed Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-Onxorg-x11-server, 0:1.20.11-8.el8_6affected
Red HatRed Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-Onxorg-x11-server-Xwayland, 0:21.1.3-2.el8_6.7affected
Red HatRed Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-Ontigervnc, 0:1.12.0-6.el8_6.18affected
Red HatRed Hat Enterprise Linux 8.8 Telecommunications Update Servicexorg-x11-server, 0:1.20.11-19.el8_8affected
Red HatRed Hat Enterprise Linux 8.8 Telecommunications Update Servicexorg-x11-server-Xwayland, 0:21.1.3-13.el8_8.1affected
Red HatRed Hat Enterprise Linux 8.8 Telecommunications Update Servicetigervnc, 0:1.12.0-15.el8_8.18affected
Red HatRed Hat Enterprise Linux 8.8 Update Services for SAP Solutionsxorg-x11-server, 0:1.20.11-19.el8_8affected
Red HatRed Hat Enterprise Linux 8.8 Update Services for SAP Solutionsxorg-x11-server-Xwayland, 0:21.1.3-13.el8_8.1affected
Red HatRed Hat Enterprise Linux 8.8 Update Services for SAP Solutionstigervnc, 0:1.12.0-15.el8_8.18affected
Red HatRed Hat Enterprise Linux 9xorg-x11-server-Xwayland, 0:24.1.9-4.el9_8.2affected
Red HatRed Hat Enterprise Linux 9xorg-x11-server, 0:1.20.11-34.el9_8.2affected
Red HatRed Hat Enterprise Linux 9tigervnc, 0:1.15.0-7.el9_8.2affected
Red HatRed Hat Enterprise Linux 9.2 Update Services for SAP Solutionsxorg-x11-server, 0:1.20.11-21.el9_2affected
Red HatRed Hat Enterprise Linux 9.2 Update Services for SAP Solutionsxorg-x11-server-Xwayland, 0:21.1.3-10.el9_2.1affected
Red HatRed Hat Enterprise Linux 9.2 Update Services for SAP Solutionstigervnc, 0:1.12.0-14.el9_2.15affected
Weakness

CWE details

CWE-121

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-121 · source CWE mapping

Stack-based Buffer Overflow

Stack-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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