Poisoned Pipeline / Incidents / AS318
CNNIC-issued intermediate ran on MCS Holdings' man-in-the-middle proxy
On 20 March 2015 Google's pinning detected a *.google.com certificate
issued by an intermediate CA chaining to CNNIC. The intermediate had been
delegated to MCS Holdings, which — contrary to its contract to issue only
for domains it registered — installed the key on its eID SSL interception
appliance instead of an HSM. The appliance issued certificates for
domains it did not control; the observed set was in a test network. Google
blocked the MCS certificate with a CRLSet push on 20 March and, after a
joint investigation, removed recognition of the CNNIC root and EV CAs in
Chrome, with a disclosed whitelist for existing certificates. Google's
post explicitly names ANSSI 2013 as the earlier instance of the same
failure.
Mapped techniques
- T0218 Compromise TLS trust identity
supply-chain MCS Holdings / CNNIC intermediate
A delegated public CA intermediate deployed on an interception
proxy. The key's holder can mint browser-valid certificates for
any domain; the root operator carries the blast radius.