A digital certificate serves as a website’s official identity card, enabling the padlock symbol in web browsers and helping ensure that connections are secure and data remains protected. However, a major security flaw was recently discovered in eight intermediate certificates issued by Indian certificate authority eMudhra. The certificates contained alarmingly weak cryptographic keys, prompting technology companies to take urgent action to prevent potential exploitation.
Security researcher Wayne alerted technology companies to the problem on October 17. To demonstrate that he had cracked the weak keys, he created a website called emudhra.we-have-a-problem.com and published a digitally signed message stating, “We have a problem here – Wayne.”
His demonstration showed that anyone possessing these keys could potentially forge trusted certificates for websites across the internet. Such certificates could allow attackers to deceive users into revealing sensitive information, including passwords and banking details.
A highly secure private key typically contains around 384 bits of complex randomness, producing a number with 116 digits that would be practically impossible for a computer to guess. In stark contrast, the compromised eMudhra keys were only between 3 and 8 bits in size.
Ben Cartwright-Cox, director of BGP.tools, described the situation as “bonkers”. He suggested that the weak keys might have originated from example code that was accidentally deployed in a live environment, expressing surprise that the mistake had gone unnoticed.
A cleanup effort potentially bigger than Heartbleed
Cryptography specialists are concerned about the lasting consequences of the vulnerability. Filippo Valsorda, an engineer working on the Go programming language, warned that resolving the issue could require a cleanup operation even larger than the notorious Heartbleed bug of 2014.
Heartbleed affected thousands of servers worldwide and took years to address because the process involved updating embedded devices and changing passwords on a massive scale.
Valsorda explained that although web browsers can be updated relatively quickly, securing overlooked Linux machines, smart-home Internet of Things devices and background server tools could take considerably longer.
How major technology companies are protecting users
Several major internet companies responded quickly to the discovery. By late Tuesday morning, Apple, Google and Mozilla had blocked the compromised certificates in Safari, Chrome and Firefox.
Cloudflare also introduced emergency fixes across its extensive network and its widely used 1.1.1.1 WARP application to protect users. Meanwhile, maintainers of the Go programming language released urgent updates for versions 1.27.3 and 1.26.10 to ensure that the compromised keys would be rejected.
Are you at risk?
So far, certificate transparency logs have shown no evidence that the weak keys were used to create malicious certificates. While this is reassuring, it does not definitively eliminate the possibility of misuse through methods that might not appear in browser-visible certificate records.
Exploiting the compromised certificates would also require an adversary-in-the-middle attack, in which a hacker positions themselves between a user and the website they are accessing. This could involve controlling the local Wi-Fi network through which the user connects.
For ordinary internet users, major technology companies have already implemented important protective measures behind the scenes. To reduce the remaining risks, users should ensure that their web browsers, smartphone operating systems and internet security applications are updated to their latest versions.
