Security · Updated 27 Oct, 11:50 pm IST
Microsoft issues out‑of‑band Windows updates to distrust eMudhra certificates
Why it matters for readers: It’s important because weak certificate keys can let attackers pretend to be real websites or software, and these updates prevent that on affected Windows machines.
- Microsoft published KB5134133 for Windows 11 (24H2, 25H2, 26H2) and KB5134125 for Windows 10 (21H2, 22H2) to distrust the affected eMudhra certificates.1
- The updates are intended for systems without Internet access, devices that cannot reach Microsoft's certificate‑update service, or where automatic Certificate Trust List updates are disabled.1
- Security teams revoked the eight eMudhra intermediate certificates after the private keys were found to be extremely weak and recoverable quickly.1
- The compromised keys, generated in April 2025, had values smaller than 256, meaning an attacker could recover them by testing only 256 possibilities.1
- Other vendors including Mozilla, Google, and Apple also began revoking the affected certificates, and Microsoft updated its Disallowed Certificate Trust List and Edge/WebView2 CRLSet to block them.1
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