Browsers block eMudhra certificates after weak keys made them forgeable

On 20 October 2026, major browser makers moved to block eight intermediate certificates issued by eMudhra — an Indian certificate authority (CA) trusted by web browsers to vouch for the identity of websites — after researchers determined their private keys were catastrophically weak. All eight used P-384 keys generated in April 2025 whose secret values were smaller than 256, meaning anyone could recover a key by testing at most 256 possibilities "almost instantly." A researcher published one of the recovered keys, for the "EM OV TLS CA - G3C" certificate, on GitHub, and BleepingComputer confirmed it matched a revoked certificate.

Because a certificate authority's intermediate certificates sit near the root of the web's trust chain, a recoverable key lets an attacker forge trusted certificates for legitimate websites and intercept otherwise-encrypted traffic without triggering browser warnings. The flaw is tracked as CVE-2026-111943.

How the weak keys were created

eMudhra attributed the problem to an error in the script used to generate the certificates, which produced a second set of weaker keys that were mistakenly selected for signing because their labels resembled those of the properly generated keys. Some of the resulting certificates were submitted to Sectigo for cross-signing, extending their reach. The company said most of the affected intermediates were never used in production and that it found no evidence they had issued certificates to end users — though researchers noted the keys could, in principle, have been recovered and abused at any point since April 2025.

Ecosystem response

Mozilla blocked the certificates through Firefox's OneCRL revocation system on 17 October 2026, without requiring a browser update or restart, and shipped Firefox 158.0.1 and ESR updates on 20 October for configurations that had missed the earlier revocation. Google Chrome blocked six TLS-authorized intermediates the same day the flaw surfaced, and Apple added protections on 19 October. eMudhra revoked all eight certificates and halted issuance under its G3 root. The Go team released versions 1.27.3 and 1.26.10, and distributions including Ubuntu, Arch Linux, Alpine, NSS, and Python's certifi shipped patches, while Debian, FreeBSD, Node.js, and Bun were still pending at disclosure. Mozilla warned that software relying on its own certificate store or skipping revocation checks — such as the macOS built-in curl — could keep trusting the certificates until updated.