Microsoft Windows updates remove trust in weak eMudhra certificates
Original title: Microsoft releases Windows OOB updates to distrust eMudhra certificates
October 26 updates target offline Windows systems after eight April 2025 intermediate keys proved recoverable.
Microsoft released out-of-band updates on October 26 that remove seven certificates tied to eMudhra hierarchies from the Windows trust list. The packages are KB5134133 for Windows 11 24H2, 25H2, and 26H2, and KB5134125 for Windows 10 21H2 and 22H2, for systems that do not get automatic certificate trust updates. Eight eMudhra intermediate private keys generated in April 2025 had values smaller than 256 and could be recovered by testing 256 numbers, which could let attackers forge certificates and intercept encrypted traffic. eMudhra revoked the intermediates; Microsoft had already disallowed them and is still reviewing remaining eMudhra roots.
Unconfirmed: The text does not say the weak keys were used in attacks; Microsoft is still reviewing remaining eMudhra roots.
- Six of the compromised intermediates were used for TLS and two for code signing.
- The update removes six eMudhra G3 roots and an AAA Certificate Services cross-sign.
- Microsoft says the same seven certificates leave the Edge trust list on October 27.
- Admins should install the update on disconnected systems and replace dependent certificates.
Impact: Forge certificates and intercept encrypted communications
| Product | Affected | Fixed in |
|---|---|---|
| Microsoft Windows 11 | 24H2, 25H2, and 26H2 | KB5134133 |
| Microsoft Windows 10 | 21H2 and 22H2 | KB5134125 |
- 1.Install KB5134133 or KB5134125 on disconnected Windows systems.
- 2.Identify certificates that depend on the removed roots and replace them if needed.
From the original article
2 min read at bleepingcomputer.com
Microsoft has released out-of-band (OOB) Windows updates to remove trust in certificates tied to compromised eMudhra certificate authority keys, protecting systems that do not receive automatic certificate trust updates. [...]
By Lawrence Abrams · bleepingcomputer.com
A short excerpt; the article and its images belong to the publisher. Summary, key facts and assessment above are AI-written from the article and can be wrong.