Microsoft suggests temporary registry hack for stricken smart card users
Summary
Microsoft deliberately changed how Windows handles RSA-based smart card certificates as part of mitigations for CVE-2024-30098, requiring Key Storage Provider (KSP) usage instead of the older Cryptographic Service Provider (CSP). That change has broken certificate operations for applications that still rely on CSP behaviour (for example signing documents, certificate-based authentication, and recognition of smart cards in some 32-bit apps).
Content summary
Microsoft acknowledges the breakage and offers a short-term workaround: set the registry value DisableCapiOverrideForRSA to 0 on affected machines. This registry tweak restores the previous behaviour until Microsoft removes the fallback in the April 2026 Windows updates. There is no long-term Microsoft-side fix — app developers must update their software to perform Key Storage Retrieval using the Key Storage API (i.e. move to KSP).
Key Points
- The change is intentional and part of a security mitigation related to CVE-2024-30098: RSA smart-card certs must use KSP rather than CSP.
- Symptoms include inability to sign documents, smart cards not recognised as CSP providers in 32-bit apps, and failures in certificate-based authentication.
- Workaround: set the registry key DisableCapiOverrideForRSA = 0 on each affected device to restore legacy behaviour temporarily.
- The registry workaround will be removed in April 2026 — it is temporary and Microsoft expects applications to be updated to use the Key Storage API/KSP.
- The issue affects almost every supported Windows and Windows Server release, and even some out-of-support builds such as Windows 10 22H2.
- Editing the registry is risky and administratively costly; organisations should avoid letting end users edit it and consider deploying the change via Group Policy or managed scripts where required.
Why should I read this?
Short version: if you run smart cards or manage machines that use certificate auth, this is one you need on your radar. Microsoft handed admins a temporary registry toggle — it fixes things for now but it’s a ticking clock to April 2026, and touching the registry is never a lovely day at the office.
Context and relevance
This is important for sysadmins, IT security teams and organisations that rely on smart-card authentication or legacy applications (particularly 32-bit apps) that haven’t migrated to the Key Storage API. The incident highlights a broader push away from CSP to KSP for stronger key handling and shows how security hardening can cause operational fallout when dependent software is not updated. Practical next steps are: identify affected apps, plan patching or updates to use KSP, and use managed deployment (GPO/scripts/endpoint management) for the temporary registry change rather than manual edits.