[NEW] [high] X.Org X11 and Xwayland: Multiple vulnerabilities allow code execution and DoS
An attacker can exploit multiple vulnerabilities in X.Org X11 and Xwayland to cause a denial of service or potentially execute arbitrary program code.
CSIRTS triage
- What
- Multiple vulnerabilities allow an attacker to cause denial of service or execute arbitrary code.
- Who is affected
- Deployments of X.Org X11 and Xwayland are affected.
- Urgency
- Remediation is urgent due to the high severity and potential for exploitation.
- Action
- Apply available patches for X.Org X11 and Xwayland.
AI-assisted analysis generated from the source advisory — verify against the original.
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Details
Original advisory: https://wid.cert-bund.de/portal/wid/securityadvisory?name=WID-SEC-2026-2240
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-559990.27% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 19% of all EPSS-scored CVEs.
- Low exploitation riskCVE-2026-560000.22% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 13% of all EPSS-scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-55999 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-56000 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
- unknownMultiple vulnerabilities in Microsoft Azure Linux (July 15, 2026)cert-fr-avis
- highCVE-2026-55999: xorg-server / xwayland glamor font atlas Heap Buffer Overflowmsrc
- unknownCVE-2026-56000: xorg-x11-server / xwayland GLX contextTags Use-After-Free in CommonMakeCurrent()msrc
- highCVE-2026-56000: Local attackers with a X connection able to provide GLX commit to the X server xorg-server bef…nvd
- highCVE-2026-55999: Local attackers with a X connection able to provide PCX fonts to the X server xorg-server befo…nvd
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