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.

slackware SSA:2026-189-03: [slackware-security] xorg-server (SSA:2026-189-03)

freebsd d6354a08-7ad4-11f1-a315-589cfc10a551: xorg-server -- Multiple vulnerabilities

There are packages installed that are affected by multiple vulnerabilities referenced in the following CVEs:

  - 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. (CVE-2026-55999)

  - Local attackers with a X connection able to provide GLX commit to the X server xorg-server before 21.2.24
    and xwayland before 24.1.13 could cause a Heap Use After Free, due to CommonMakeCurrent() pointing into
    potentially reallocated memory. (CVE-2026-56000)

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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. (CVE-2026-55999)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Severity
444516	Alpine: multiple xwayland packages: security update to 24.1.13-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	critical
444516	Alpine: multiple xwayland packages: security update to 24.1.13-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	critical
444515	Alpine: multiple xorg-server packages: security update to 21.1.24-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	critical
444515	Alpine: multiple xorg-server packages: security update to 21.1.24-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	critical
325681	Linux Distros Unpatched Vulnerability : CVE-2026-55999	Nessus	Misc.	high

Detections

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CVE-2026-55999

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