eMudhra Issues Flawed Certificates, Creating Global Security Risk
Eight CA certificates issued by eMudhra with one-byte private keys allow attackers to impersonate any domain or sign malicious code as legitimate.
By Kavya Kapoor ·
An Indian certificate authority has issued eight flawed certificates that could allow attackers to impersonate any website or sign malicious software as legitimate. The certificates, issued by eMudhra, contain private keys only one byte long, making them trivial to guess. Systems administrators and software vendors are now racing to update devices and applications to block the compromised keys.
The flaw affects six TLS intermediate certificates and two code-signing intermediate certificates. A private key is the secret half of a certificate pair, but in this case, the keys were only one byte long, meaning they consist of a number from 0 to 255. Such keys can be brute-forced in a fraction of a second. How eMudhra produced such weak keys remains under investigation.
Software verifies a certificate's legitimacy by checking its chain. A website's certificate is issued and signed by an intermediate certification authority, whose certificate is in turn trusted and signed by root certificates. The private keys for root certificates are typically kept offline. In this case, eMudhra issued intermediate certificates with guessable keys, breaking the chain of trust.
An attacker positioned in a network path, such as a public Wi-Fi hotspot or an internet service provider, could intercept a connection and impersonate any website. An operating system or application that has not been updated would not detect the substitution. Code-signing certificates pose a similar threat, as downloaded applications could appear to come from Microsoft or Google when they do not.
Operating systems and applications maintain lists of trusted root certificates and certification authorities. Browsers also keep a revocation list of certificates not to trust. These lists are updated when problems arise, and they must now be updated again to revoke the eight affected keys or remove the compromised root certificate.
Recent versions of Chrome, Brave, Firefox, and Safari enforce Certificate Transparency, which consults a public log of certificate issuances and blocks any not listed. Google reported that no certificates signed by the affected intermediate CAs were logged in that system, so regular web browsing should remain safe. Users should still update software to protect against other forms of attack.
The scale of the required updates spans personal computers, servers, operating systems, phones, tablets, routers, web browsers, virtual servers, virtual machines, containers, and programming languages such as Python, Go, Node.js, and Rust. Standalone download utilities like curl are also affected. Older routers, smart devices, and older computers may present problems if they do not receive updates.
No specific reactions from eMudhra or affected software vendors were included in the source material. The investigation into how the one-byte keys were generated continues.
Users should update operating systems, browsers, and applications as updates become available. Systems administrators should apply patches to servers and network equipment. Developers should update dependencies and libraries that handle certificate validation. No specific timeline for remediation was provided in the source material.
Source: Tom's Hardware
