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CVE Record

CVE-2025-26596: Xorg: xwayland: heap overflow in xkbwritekeysyms()

A heap overflow flaw was found in X.Org and Xwayland. The computation of the length in XkbSizeKeySyms() differs from what is written in XkbWriteKeySyms(), which may lead to a heap-based buffer overflow.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2025-26596 is a memory corruption flaw in X.Org and Xwayland. A local authenticated user could potentially crash or compromise a graphical server process, with high impact to confidentiality, integrity, and availability. Treat this as important for Linux desktops, VDI, and GUI-enabled servers.

Executive priority

High priority for Linux estates with desktops, VDI, VNC, or shared graphical systems. This is not shown as remotely exploitable from the supplied evidence, but the potential impact is high once a local user has access.

Technical view

The flaw is a heap-based buffer overflow, CWE-787, caused by inconsistent length computation between XkbSizeKeySyms() and XkbWriteKeySyms(). The supplied CVSS 3.1 vector is 7.8 high: local attack, low complexity, low privileges, no user interaction, and high CIA impact.

Likely exposure

Exposure is most likely on systems running affected X.Org, Xwayland, or TigerVNC packages, especially listed Red Hat Enterprise Linux streams and Debian LTS environments. Internet-facing exposure is not established by the supplied sources; the CVSS vector indicates local access is required.

Exploitation context

The bundle does not identify active exploitation, public exploit use, or CISA KEV listing. Practical risk is highest where untrusted or many users can access graphical sessions, remote desktop services, or multi-user Linux systems with vulnerable packages installed.

Researcher notes

Do not infer broader product impact beyond X.Org, Xwayland, TigerVNC, and named vendor packages in the bundle. The sources support a heap overflow and high CVSS rating, but do not provide exploit telemetry or weaponized details.

Mitigation direction

  • Apply relevant vendor security updates from Red Hat, Debian, or your distribution vendor.
  • Prioritize GUI servers, VDI hosts, remote desktop systems, and multi-user Linux environments.
  • Restrict local account access to affected systems until updates are applied.
  • Check vendor guidance before applying non-vendor workarounds or backports.
  • Restart affected graphical sessions or services after package updates where required.

Validation and detection

  • Inventory xorg-x11-server, xorg-x11-server-Xwayland, and tigervnc packages across Linux hosts.
  • Compare installed package versions against the listed Red Hat errata and distribution advisories.
  • Confirm vulnerability scanners map findings to CVE-2025-26596 and affected package names.
  • Verify updated packages are installed after remediation.
  • Review logs for unusual Xorg, Xwayland, or VNC crashes, without treating crashes as proof of exploitation.
Prepared
Confidence
high
Sources
11

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-787: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2025-26596 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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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.

1CVSS vectors
5Timeline events
2ADP providers
19Source links

SSVC decision data

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

CVSS vector scores

1 official score

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

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2025-26596Attack 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. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. Source timelineredhat

    Reported to Red Hat.

  3. Source timelineredhat

    Made public.

  4. CVE publishedCVE Program

    The CVE record was published.

  5. CVE updatedCVE Program

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

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Unknown vendorxserverxserver, 0, 22.0.0unaffected
Red HatRed Hat Enterprise Linux 10xorg-x11-server-Xwayland, 0:24.1.5-3.el10_0affected
Red HatRed Hat Enterprise Linux 6 Extended Lifecycle Support - EXTENSIONtigervnc, 0:1.1.0-25.el6_10affected
Red HatRed Hat Enterprise Linux 7 Extended Lifecycle Supporttigervnc, 0:1.8.0-36.el7_9affected
Red HatRed Hat Enterprise Linux 7 Extended Lifecycle Supportxorg-x11-server, 0:1.20.4-30.el7_9affected
Red HatRed Hat Enterprise Linux 8tigervnc, 0:1.13.1-15.el8_10affected
Red HatRed Hat Enterprise Linux 8.2 Advanced Update Supporttigervnc, 0:1.9.0-15.el8_2.13affected
Red HatRed Hat Enterprise Linux 8.4 Advanced Mission Critical Update Supporttigervnc, 0:1.11.0-8.el8_4.12affected
Red HatRed Hat Enterprise Linux 8.4 Telecommunications Update Servicetigervnc, 0:1.11.0-8.el8_4.12affected
Red HatRed Hat Enterprise Linux 8.4 Update Services for SAP Solutionstigervnc, 0:1.11.0-8.el8_4.12affected
Red HatRed Hat Enterprise Linux 8.6 Advanced Mission Critical Update Supporttigervnc, 0:1.12.0-6.el8_6.13affected
Red HatRed Hat Enterprise Linux 8.6 Telecommunications Update Servicetigervnc, 0:1.12.0-6.el8_6.13affected
Red HatRed Hat Enterprise Linux 8.6 Update Services for SAP Solutionstigervnc, 0:1.12.0-6.el8_6.13affected
Red HatRed Hat Enterprise Linux 8.8 Extended Update Supporttigervnc, 0:1.12.0-15.el8_8.12affected
Red HatRed Hat Enterprise Linux 9tigervnc, 0:1.14.1-1.el9_5.1affected
Red HatRed Hat Enterprise Linux 9xorg-x11-server, 0:1.20.11-28.el9_6affected
Red HatRed Hat Enterprise Linux 9xorg-x11-server-Xwayland, 0:23.2.7-3.el9_6affected
Red HatRed Hat Enterprise Linux 9.0 Update Services for SAP Solutionstigervnc, 0:1.11.0-22.el9_0.13affected
Red HatRed Hat Enterprise Linux 9.2 Extended Update Supporttigervnc, 0:1.12.0-14.el9_2.10affected
Red HatRed Hat Enterprise Linux 9.4 Extended Update Supporttigervnc, 0:1.13.1-8.el9_4.5affected
Red HatRed Hat Enterprise Linux 6xorg-x11-serverunknown
Red HatRed Hat Enterprise Linux 8xorg-x11-serverunaffected
Red HatRed Hat Enterprise Linux 8xorg-x11-server-Xwaylandunaffected
Weakness

CWE details

CWE-787

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

CWE-787 · source CWE mapping

Out-of-bounds Write

Out-of-bounds Write represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs