You don't have to think about it too hard, there's companies that will help you with the transaction. https://www.zerodium.com/
Notice also that with just a couple exceptions, RCEs in extremely widespread serverside web components are valued at $10k (if you believe their price list; I'm skeptical of it). Those are vulnerabilities that all have half-lives after patches are issued --- that's a ceiling for what anything like this could be worth.
Second, Zerodium isn't "the black market".
In the scenario you described, without any other contacts and/or experience with transactions like this, I would approach an exploit broker. As for the payout - I assumed that any RCE vulnerability that qualifies for Google's highest bounty is likely to fetch a higher price elsewhere.
My experience with the field is limited and considering yours, if you are suggesting that this particular exploit would not fetch a significantly higher price, I shall stand corrected.
I'm not quite sure what you're getting at here. If you're trying to point out that I haven't done my homework on this and that I don't have a sufficiently specific/workable plan how to approach it - that is accurate. I don't have exploits to sell.
In my previous comment I already stated the assumption that I made, if you feel it's incorrect, which clearly you do, feel free to correct/fill in whatever you think is missing. I'm not getting into a debate about something with which I don't have in-depth experience with someone who does.
I think a lot of HN'ers believe that there's a market for high-severity bugs of any ilk, when, in reality, there's really only a liquid market for a pretty specific subset of those bugs.
As for the black market price - I don't consider my security background sufficient for my guess to be anywhere near educated enough, so I'm bowing out.
And not to spoil the game, but the subset of vulns that fetch good money has only narrowed in the last years as exploit mitigation has improved. The true unicorn 0days of yesteryear are almost always multiple hard earned bugs these days. Bugs in one vendor's project, even Google, it is cool they have such a high end reward, let alone 36k. Unless you crossed a line and exfiltrated data (high risk), I can't imagine getting this much money anywhere else.
Amusingly, 36k does look very similar to ~3wks of boutique infosec consulting, though, so for Google the price while generous probably makes sense.
Known security person buys this in order to turn it in themselves for a higher bounty and increased rep.
I guess Zerodium has enough reputation that you can be reasonably sure they'll fork over the cash after you show them your bug. Building that kind of reputation on the darknet with cryptocurrency isn't going to be easy. If there was anyone like that out there, we'd already know about them.
BTW -- not to fan out too hard, but I put together the pieces recently and realized in addition to Latacora you worked on Cryptopals and Microcorruption. As someone interested in exactly those areas with little knowledge of how to break in, thank you! I've found both great learning resources (although I'm embarrassingly early in the crypto challenges still..)
In the GAE case, Google can patch all deployments of their service on the same day, which is an "instantaneous fix".
If it were an RCE with a webserver, OS or some other popular software, that can't be patched "instantaneously" "worldwide". Each entity who maintains their own (i.e. nginx, Drupal, Redis, etc.) instance needs to be alerted to the patch and then apply it. That's an incredibly long tail.
Or else, why do buyers want clients?
The hypothesis I like to come back to --- I'm pretty sure it's true --- is that vulnerabilities have value on the black market only if they fit into an existing business model, such that they can be dropped in and immediately be used to make money. People have to already be using some other vulnerability to do the exact same thing, and reliably making money with it.
People on HN like to tell stories about how a master criminal could make money with everything from Facebook CSRFs to serverside RCEs. But none of those kinds of exploits support current ongoing business concerns; they're all one-of-a-kind. Nobody buys a vulnerability speculatively to see if they might make a go of it --- they especially don't do that for a vulnerability that could be extinguished universally in moments by Google or Facebook's security team.
I could see an argument here towards the market price of the information -- breaching a company in the above scenario might get you zilch. Breaking an iOS device of an individual of interest gets you a lot of value.
Circling back though -- you're saying that this model isn't one in use. Do you agree with my real-life counterpoint? If so, why wouldn't there be a market? Or, is the market there and the low payouts from the likes of Zerodium reflect the actual low value of the product (and by extension, business model)?
There are, of course, real brokers who will buy zero-day vulnerabilities for use by national IC's and LEO's. Their names don't get around like Zerodium's --- Zerodium sponsors conferences --- but they're not hard to find.
If you've got the kind of bug that these firms buy --- essentially, clientside RCE in hugely popular platforms --- you can probably do better selling to them than you can by collecting bounties from the vendors directly. It takes some moral flexibility, though, since really what you're doing is profiting from other people's exposure, and, especially with mobile clientside RCE, what you're really really doing is getting dissidents in Western-friendly dictatorships imprisoned. But you can do that.
But none of these firms (that I know) buy one-off vulnerabilities like a GCE RCE. All the vulnerabilities with high market values have half-lives, which is to say that even after they're patched, it will take weeks, months, or sometimes even years to see them eradicated, which gives them the residual value that props up their market price. In contrast to that, a GCE RCE that was actually exploited would be detected pretty quickly, and shut down with finality in a matter of hours.
And, really, dictators don't need help imprisoning dissidents -- it's sort of in the jobspec. It's not likely that a vuln would cause this to happen unless it was in systems created and secured specifically for sedition, in which case a researcher should be considerate of the potential damage.
I would find it morally offensive but I'm a naive country bumpkin I guess. I have pointed out something that was mispriced rather than profit from their error. It cost me something like ~$50-100 extra but I slept better.