I think this is it. I think it needs to be worded: "There are 30,000 certificates which no one knows for sure the validity of, and thus need to be revalidated." The 127 merely proved that misissuance was quite possible, and did happen numerous times.
EDIT: I think that's really the crux of the issue. These 127 certs which Symantec claims are "harmless" are merely the ones which were stumbled across and obviously very "how is this even possible" wrong.
That's why the 30,000 is the "size of the risk". The big "Symantec" problem is that there's no good way to distinguish these 30,000 from the many more certificates issued by Symantec under different brands. For Google it's all-Symantec-or-nothing. So they're coming up with measures that apply to all-Symantec.
Any further detail from Ryan or anyone else involved here would be very helpful (their are plenty of other organizations who bootstrap based on Google/Mozilla/Microsoft/Apple's root CA program)
Though it doesn't mention the 30000 certs or 127 certs, it does say:
(long quote from Ryan Sleevi:)
In the current misissuance, my understanding is that Symantec asserts that
the totality of the misissuance was related to RAs. Symantec's initial
response to the set of questions posed by Google [5] indicated that " At
this time we do not have evidence that warrants suspension of privileges
granted to any other RA besides CrossCert" in the same message that
provided the CP/CPS for other RAs besides CrossCert, and itself a follow-up
to Symantec's initial response to the Mozilla community, [6], which
acknowledged for the potential of audit issues in the statement "We are
reviewing E&Y’s audit work, including E&Y’s detailed approach to
ascertaining how CrossCert met the required control objectives.". This
appears to be similar to the previous event, in that the proposed
remediation was first a termination of relationship with specific
individuals. However, in Symantec's most recently reply, [1], it seems that
again, on the basis of browser questions from a simple cursory examination
that such a statement was not consistent with the data - that is, that the
full set of issues were not identified by Symantec in their initial
investigation, and only upon prompting by Browsers with a specific deadline
did Symantec later recognize the scope of the issues. In recognizing the
scope, it was clear that the issues did not simply relate to the use of a
particular RA or auditor, but also to the practices of RAs with respect to
asserting things were correct when they were not.
It appears that, similar to the Testing Tool's failure to ensure that
certificates were adhering to the fulsome standards of authentication,
Symantec's newly established compliance team was failing to perform even a
cursory review of the CP, CPS, and audit statements presented - despite
Symantec having found it necessary in that introspective process themselves
in response to [3], as noted above.
Symantec's also stated that, in response to the past misissuance, it
deployed a compliance assessment tool, which functionally serves a role
similar to a Validation Specialist. However, such compliance assessment was
designed in a way that it could be bypassed or overridden without following
appropriate policies.
The major CAs outsource to partner companies called Registration Authorities (RAs) to perform the task of verifying that people requesting certs are who they say they are --- this is especially important for markets where the company running the CA is has thin on-the-ground support. Such is the case with Symantec/Verisign and CrossCert, their partner RA in Korea.
The technical relationship between the RA and the CA probably varies a lot from firm to firm, but generally the RA has some ability to cause issuance of certificates through automated requests to the CA's infrastructure.
What Ryan and others discovered in repeated rounds of questioning to Symantec was that Symantec had been relying entirely on 3rd party WebTrust audits (these are technical and process audits for CAs conducted by Big 5 accounting firms) without doing any of its own technical due diligence. But the WebTrust audits Symantec's RA's had been doing were delivered by auditors nobody has any faith in, including (as it turns out) Symantec.
Further, Symantec was required to have technical and process controls for specific kinds of issuance requests from their RAs. And it did. But it turned out those controls were designed so that the RAs could override them on their own recognizance. Which is basically the same as running process controls on the honor system --- not OK in this environment.
Didn't E&Y feature as auditors in the WoSign/StartCom incident as well? Perhaps that decision to only refuse to accept audits from the Hong Kong branch of E&Y wasn't such a great idea...
_Some_ major CAs outsource like this. You need this sort of on-the-ground stuff, particularly human employees who can speak the local language and understand local culture, to validate certain subject details, it's not important for the domain validation that most of us care about most of the time. Knowing if the subscriber is really Foo Corp of Shanghai, requires local knowledge, but checking foo-corp-shanghai.example is controlled by the subscriber needs, at the very most, a translated web page of instructions which you can out-source.
It is likely Mozilla policy (or the BRs) will forbid letting the local RA do the domain validation. So, a future CrossCert could lie about whether their subscriber is really Foo Corp, but not about whether they control foo-corp.example
Oh, and it's not the Big Five any more, one of the Five collapsed in scandal because it happily signed off on Enron's obviously bogus accounts. So now we have a Big Four, until another one blows up. For those taking bets, the RA was audited by a local EY, whereas Symantec are audited by a KPMG.
EDIT: I think that's really the crux of the issue. These 127 certs which Symantec claims are "harmless" are merely the ones which were stumbled across and obviously very "how is this even possible" wrong.
That's why the 30,000 is the "size of the risk". The big "Symantec" problem is that there's no good way to distinguish these 30,000 from the many more certificates issued by Symantec under different brands. For Google it's all-Symantec-or-nothing. So they're coming up with measures that apply to all-Symantec.