WSUS is enterprise-wide; remote code execution could disrupt patch management across many organizations.
CVE-2026-20856
RCE via WSUS due to improper input validation.
Is CVE-2026-20856 being exploited?
Not confirmed. CVE-2026-20856 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 1.1% probability of exploitation in the next 30 days.
How severe is CVE-2026-20856?
CVE-2026-20856 is rated High with a CVSS score of 8.1. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-20856?
Yes. A fix has been recorded for CVE-2026-20856. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-20856 affect?
CVE-2026-20856 affects Windows Server with WSUS. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-20856?
Apply the Microsoft WSUS security update promptly.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution over the network on WSUS; attacker can run arbitrary code on affected servers.
Immediate action required
- affected>= 10.0.14393.0 and < 10.0.14393.8783
- affected>= 10.0.17763.0 and < 10.0.17763.8276
- affected>= 10.0.19044.0 and < 10.0.19044.6809
- affected>= 10.0.19045.0 and < 10.0.19045.6809
- affected>= 10.0.22631.0 and < 10.0.22631.6491
- affected>= 10.0.22631.0 and < 10.0.22631.6491
- affected>= 10.0.26100.0 and < 10.0.26100.7623
- affected>= 10.0.26200.0 and < 10.0.26200.7623
- affected>= 6.2.9200.0 and < 6.2.9200.25868
- affected>= 6.3.9600.0 and < 6.3.9600.22968
- affected>= 6.3.9600.0 and < 6.3.9600.22968
- affected>= 6.2.9200.0 and < 6.2.9200.25868
- affected>= 10.0.14393.0 and < 10.0.14393.8783
- affected>= 10.0.14393.0 and < 10.0.14393.8783
- affected>= 10.0.17763.0 and < 10.0.17763.8276
- affected>= 10.0.17763.0 and < 10.0.17763.8276
- affected>= 10.0.20348.0 and < 10.0.20348.4648
- affected>= 10.0.25398.0 and < 10.0.25398.2092
- affected>= 10.0.26100.0 and < 10.0.26100.32230
- affected>= 10.0.26100.0 and < 10.0.26100.32230
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.