One-Byte eMudhra Certificate Keys Trigger Revocations and Software Updates
Summary
A script generated eight eMudhra intermediate certificates with one-byte private keys, which a researcher recovered. Root stores and software projects are blocking or removing the certificates; eMudhra says none issued end-entity certificates.
Key points
- eMudhra said a script deployed in April 2025 generated eight weak intermediate certificates that were mistakenly used for signing because their key labels were similar.
- The private key values ranged from 0 to 255; researcher Scott Helme recovered the keys. The certificates use elliptic-curve cryptography intended to use 48-byte keys.
- Cloudflare warned the certificates could be used to impersonate servers and intercept or modify traffic. eMudhra said only one certificate reached production and none issued certificates for end entities.
- Six certificates were for TLS and trusted by the Chrome, Mozilla, Microsoft, and Apple root stores; two were for code signing and trusted by Microsoft.
- Browser vendors and Sectigo revoked or blocked the certificates. Google said revocation would reach affected devices by Oct. 27; Google is also reviewing eMudhra's remaining certificates in its root store.
- Go, Python, Rust, Red Hat Linux, and Ubuntu issued or announced updates; a Java patch was listed as pending. The issue is tracked as CVE-2026-111943 in the Go ecosystem.
- eMudhra estimated that 30,000 certificates must be migrated. India's Ministry of Electronics and Information Technology opened an investigation.
Article Details
- Vulnerability Types
- Certificate authority generated intermediate certificates with private encryption keys only one byte long instead of the intended 48 bytes, allowing the keys to be recovered and fraudulent certificates to be issued.
- Exploitation Status
- not_reported
- Exploit Availability
- unknown
- Patch Status
- partial
- Workarounds
- RedHat Linux users were advised to consider disabling the eMudhra certificates until a patch is available.
CVE
People
Dennis JacksonMozilla senior staff cryptography engineer who discussed the affected certificates and recovery of their keys.Scott HelmeSecurity researcher who cracked the deficient certificates and recovered their private key values.WayneResearcher who first notified the Chrome Root Program about the weak certificates.Yash KadakiaSecurity Brigade founder and CTO who commented on the incident and called for a review of mandatory security audits.
Vendors
eMudhraThe firm, Bengaluru-based eMudhra, said a script deployed in April 2025 generated the weak certificates, which were mistakenly used that month for certificate signing "because the key labels were similar."SectigoDigital certificate provider Sectigo, which in May 2025 cross-signed each of the deficient certificates, revoked the certificates on Monday. Newer certificate authorities such as eMudhra often do a business deal with
Products
GoThe Go programming language on Monday told users that it is "blocking trust in a small set of intermediate certificates due to specific security concerns around their operation" and "highly recommending" upgrading to aGoogle Chromethe weak certificates are for web cryptographic protocol TLS and trusted by the four major root stores, Chrome, Mozilla, Microsoft and Apple. The other two certificates are for code signing and were trusted byMozilla FirefoxFirefox and Chrome blocked the certificates on Saturday. They also blacklisted the root eMudhra certificate used to sign the eight intermediate certs, with Google's revocation expected to reach all affected devices byPythonPython core developers on Tuesday told programmers "to immediately upgrade" to a new version to remove the affected certificates. Maintainers of Rust similarly released a Tuesday patch. Makers of RedHat Linux on MondayRed Hat Enterprise Linuxto remove the affected certificates. Maintainers of Rust similarly released a Tuesday patch. Makers of RedHat Linux on Monday advised users to apply a patch "as soon as it is available" and in the meantime to considerRustprogrammers "to immediately upgrade" to a new version to remove the affected certificates. Maintainers of Rust similarly released a Tuesday patch. Makers of RedHat Linux on Monday advised users to apply a patch "asUbuntuapply a patch "as soon as it is available" and in the meantime to consider disabling the eMudhra certs. Ubuntu maintainers released a patch on Tuesday. A patch for the Java programming language is listed as "pending"