EUVD-2026-56649
GHSA-3v6v-6vwq-2h95
Severity by source
AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Network vector with high complexity and required user interaction matches JWT-based bypass requiring attacker-victim interaction; no confidentiality or availability impact, integrity impact is high due to authentication bypass.
Primary rating from Vendor (microsoft).
CVSS VectorNVD
Lifecycle Timeline
4DescriptionNVD
Improper verification of cryptographic signature in Windows Schannel allows an unauthorized attacker to bypass a security feature over a network.
AnalysisAI
Authentication bypass in Windows Schannel allows a network-based attacker to circumvent cryptographic signature validation, achieving high-integrity impact without requiring prior privileges. Schannel, Microsoft's TLS/SSL security provider, fails to properly verify cryptographic signatures - tagged as a JWT attack vector - enabling forged or malformed tokens to pass validation and bypass security feature enforcement. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires high attack complexity (AC:H per CVSS), meaning specific conditions must exist rather than a simple opportunistic probe. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 5.3 medium score reflects real mitigating factors: AC:H signals high attack complexity requiring specific conditions to be met, and UI:R indicates user interaction is necessary - two constraints that substantially reduce the exploitability window beyond what the I:H (high integrity impact) alone might suggest. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Microsoft has released patches for all affected Windows versions via the standard Windows Update mechanism; administrators should apply the monthly cumulative update containing fixes to the respective build thresholds listed above. … Detailed patch versions, workarounds, and compensating controls in full report. |
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External POC / Exploit Code
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