Affects Microsoft Windows Schannel (widely deployed TLS/SSL stack); high-severity info disclosure in a core OS component merits broad attention.
CVE-2026-56186
Out-of-bounds read in Windows Schannel enables remote information disclosure.
Is CVE-2026-56186 being exploited?
Not confirmed. CVE-2026-56186 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-2026-56186?
CVE-2026-56186 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-2026-56186?
Yes. A fix has been recorded for CVE-2026-56186. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-56186 affect?
CVE-2026-56186 affects Microsoft Windows Schannel (TLS/SSL), Windows Server builds using Schannel, Windows client builds using Schannel. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-56186?
Apply Microsoft security updates when released; limit external access to TLS services; monitor for anomalous TLS activity.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authorized remote attacker can trigger an out-of-bounds read in Schannel to disclose memory contents (credentials, keys, sensitive data) over the network.
Patch when possible
- affected>= 10.0.14393.0 and < 10.0.14393.9339
- affected>= 10.0.17763.0 and < 10.0.17763.9020
- affected>= 10.0.19044.0 and < 10.0.19044.7548
- affected>= 10.0.19045.0 and < 10.0.19045.7548
- affected>= 10.0.26100.0 and < 10.0.26100.8875
- affected>= 10.0.26200.0 and < 10.0.26200.8875
- affected>= 10.0.28000.0 and < 10.0.28000.2525
- affected>= 6.2.9200.0 and < 6.2.9200.26226
- affected>= 6.3.9600.0 and < 6.3.9600.23291
- affected>= 6.3.9600.0 and < 6.3.9600.23291
- affected>= 6.2.9200.0 and < 6.2.9200.26226
- affected>= 10.0.14393.0 and < 10.0.14393.9339
- affected>= 10.0.14393.0 and < 10.0.14393.9339
- affected>= 10.0.17763.0 and < 10.0.17763.9020
- affected>= 10.0.17763.0 and < 10.0.17763.9020
- affected>= 10.0.20348.0 and < 10.0.20348.5386
- affected>= 10.0.26100.0 and < 10.0.26100.33158
- affected>= 10.0.26100.0 and < 10.0.26100.33158
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.