Cloudflare Finds Forged Certificates After eMudhra Weak-Key Exposure

Summary

Cloudflare reports forged certificates using eMudhra’s weak keys, but no evidence of intercepted connections. Its probes suggest many clients, including 30–40% of Android WebView traffic, still accept the compromised chain; bot-heavy traffic limits certainty.

Key points

Cloudflare says eMudhra’s eight weak intermediate keys could be recovered from public certificates and used to create certificates that unpatched clients might accept.
Cloudflare says all its high-priority systems were patched to reject the weak keys; a small number of confirmed, low-impact tickets remained in progress.
Cloudflare logged about 22,000 attempted handshakes involving the weak keys. Roughly two-thirds were test-site fetches; most of the rest appeared to involve origins using certificates created for themselves.
About 160 certificates had subject names unrelated to the requested server names. Cloudflare found no evidence these were used to intercept its connections, though some appeared to have been forged soon after the weakness became public.
In 50 million challenge-page probes, Cloudflare found that up-to-date browsers were mostly patched, while 30–40% of Android WebView traffic still accepted the compromised chain. The sample was skewed by bots and changing traffic classifications.
Cloudflare urges users to patch and says it is exploring wider use of quick certificate-revocation mechanisms.

Article Details

Vulnerability Types: Extremely weak certificate-authority intermediate signing keys, recoverable from public certificates
Exploitation Status: reported
Exploit Availability: unknown
Patch Status: available
Workarounds: Patch client systems so they reject the weak eMudhra keys.

People

Dennis JacksonProvides a crowdsourced website with instructions for patching systems affected by the weak keys.

Vendors

CloudflarePatching Cloudflare eMudhraOn October 19, 2026, we learned about eMudhra’s eight shockingly weak keys: where eMudhra was trusted to pick a 115-digit number for their virtual combination lock protecting the Internet, they picked the number 4. Not

Products

Android WebViewmodern browsers are mostly patched, but bots and old browsers are not. Also embedded browsers, like Android WebView, lag behind patching with 30–40% still accepting. Over the first weekend (with the monitoring gap),Google Chrome29 around 18:00 UTC, we released a detection that caught a large influx of bot traffic identifying as Chrome 150-154 on macOS. This can look like patching in the top graph, but it is actually a change in traffic Pingorahigh-impact systems immediately on October 19. These included customer origin-facing proxies using Pingora, responsible for most of our outbound connections. These were patched in hours to reject the vulnerable