Eight private keys belonging to Indian certificate authority eMudhra were compromised, potentially allowing attackers to forge certificates and impersonate trusted websites. Major browser makers quickly blocked the certificates, and no attacks have been reported, but some nonbrowser software may remain vulnerable because it does not check whether certificates have been revoked.
Researchers said eMudhra used easily guessed integers as private keys, enabling all eight to be recovered from public certificates in under a second.
Discovery and response
The issue came to light on Oct. 17, when a researcher named Wayne reported the flaw to browser makers. To prove the vulnerability, Wayne used all eight compromised keys to digitally sign his warning message: "We have a problem here – Wayne."
Browser makers and software developers have pushed out emergency fixes since then. Mozilla received the report just after 8 p.m. UTC and had a block in place about three hours later. Chrome blocked the certificates the same day. Apple followed on Oct. 19 and Microsoft on Oct. 20. eMudhra has also revoked the certificates.
Mozilla warned that network interceptors could use these fraudulent certificates to impersonate trusted sites, allowing them to read or alter the user's data.
How the keys were compromised
How the keys got out is still unclear. According to researchers, eMudhra used tiny integers like 4, 56, and 237 as private keys instead of strong 384-bit random numbers. Security researcher Scott Helme went further, writing: "One of eMudhra's certificate authority private keys is the number 4. Another one is 56, and another is 115."
A proper key is a huge random number that no one could guess. Helme says he recovered all eight from public certificates in under a second, and that the keys have been exposed since April 2025.
Helme's reading of a Mozilla bug ticket says eMudhra blamed a bug in its key-setup script.
Broader risks
Browsers are mostly safe now, but the bigger worry is other software. Many programs never check whether a certificate has been revoked. "So the fact that eMudhra and Sectigo have revoked these intermediates doesn't help them at all," Helme wrote.
He says his tests showed tools like curl, Python, Node, Go and Java accepted a forged certificate for Stripe's API. Fixes are out for Go, Python's certifi package and Rust's webpki-roots. Node.js was still pending when last checked.
Crypto users should care about this too, mostly outside the browser. Exchange bots, trading scripts and wallet backends often run on Python, Node or Go. A forged certificate for an exchange's API could let an attacker on the same network read or change a bot's traffic. No crypto attacks have been reported, and no attacks on users have been reported so far.
CoinDesk contacted eMudhra for comment.
