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    CVE-2026-55999

    Local attackers with a X connection able to provide PCX fonts to the X server xorg-server before 21.2.24 and xwayland before 24.1.13 could cause a heap buffer overflow via SetFont due to missing glyph boundary checks.

    Published:Jul 8, 2026
    Last Modified:Jul 8, 2026
    EPS:Jul 8, 2026
    EPSS Score:0.00284
    CVSS Score:8.5

    Affected Products

    Vendor
    X.org
    Product
    Xorg-server
    Vendor
    X.org
    Product
    Xwayland

    Exploits

    No exploit reference

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-100 Overflow Buffers
    CAPEC-256 SOAP Array Overflow
    CAPEC-92 Forced Integer Overflow

    Related CVEs

    CVE-2026-56000 (CVSS 9) — Local attackers with a X connection able to provide GLX commit to the X server xorg-server before 21.2.24 and …
    CVE-2026-50259 (CVSS 7.8) — A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. _XkbSetMapChecks() declares a…
    CVE-2026-50262 (CVSS 5.5) — An out-of-bounds read flaw was found in the X.Org X server and Xwayland in __glXDisp_ChangeDrawableAttributes(…
    CVE-2026-50257 (CVSS 7.8) — A use-after-free flaw was found in the X.Org X server and Xwayland in miSyncDestroyFence(). A client that sets…
    CVE-2026-50260 (CVSS 7.8) — A use-after-free flaw was found in the X.Org X server and Xwayland in FreeCounter(). A client that sets up mul…
    CVE-2026-50264 (CVSS 7.8) — An out-of-bounds write flaw was found in the X.Org X server and Xwayland in DRIGetBuffers/DRIGetBuffersWithFor…
    CVE-2026-50261 (CVSS 7.8) — A use-after-free flaw was found in the X.Org X server and Xwayland in SyncChangeCounter(). A client that sets …
    CVE-2026-50256 (CVSS 7.8) — A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. A mismatch between the X serv…
    CVE-2026-34000 (CVSS 6.1) — A flaw was found in the X.Org X server. This out-of-bounds read vulnerability in the XKB geometry processing, …
    CVE-2015-3164 (CVSS 3.6) — The authentication setup in XWayland 1.16.x and 1.17.x before 1.17.2 starts the server in non-authenticating m…

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High