Mozilla patches Wednesday’s Pwn2Own double-exploit… on Friday!

Security

Just a short note to let you know that we were wrong about Firefox and Pwn2Own in our latest podcast…

…but we were right about how Mozilla would react in our latest podcast promotional video:

In the video, we said (our own emphasis below):

In the podcast, we speculated, “Was this [recent Firefox fix] pushed out just in time for Pwn2Own, in the hope that it would prevent the attack working?” If that was the reason, it didn’t work. […] But we do know that Mozilla will be rushing to fix this one as soon as they get the details out of the Pwn2Own competition.

To explain.

In an article last weekend, after our Linux distro had received an apparently-hurried out-of-band Firefox patch but the update still hadn’t shown on on Firefox’s website, we found ourselves wondering, “Is there some kind of cybersecurity scramble on here?”

This update added a sandbox security feature known as Win32k Lockdown that had been months, if not years, in the making, but had just missed schedlued release 100.0.

Accordingly, we speculated that Firefox 100.0.1, a mere point-release in which a brand new Windows security feature had suddenly been activated, was wrangled out specially, just in time for this year’s Pwn2Own hacking competition in Vancouver, Canada.

Why not wait?

We were surprised that Mozilla didn’t simply wait until the next scheduled release, 101.0, to turn the new feature on and announce it as a feature, rather than as a “security fix”, givem that it wasn’t there to stop a clear and specific attack that was already known.

Usually, point releases come out to deal with urgent issues that genuinely can’t wait, such as new features that flop, or zero-day bugs that suddenly show up in the wild and need dealing with before the next four-weekly major update deadline rolls around.

But with Pwn2Own taking place this very week, and with Firefox in the firing line from experienced and successful bug hunter Manfred Paul, maybe Mozilla figured that it was worth squeezing out 100.0.1 in time for the contest?

Just in case the new sandbox feature might throw an unexpected spanner into Paul’s otherwise-certain-to-succeed hacking session, and save the day?

On Wednesday, Paul’s session started with 30’00” on the clock, counting downwards (a hard upper bound of 30 minutes is imposed for each entrant).

After a brief pause, the adjudicator reached out and clicked a button to initiate the hacking attempt by visting a URL that was ready to unleash Paul’s double-exploit remotely. (The server was remote in network terms; physically it was on the same table as the client under attack.)

Loosely speaking, Paul planned to break into Firefox, earning $50,000 in bug bounty for remote code execution, and then to break back out of it, earning another $50,000 for a full sandbox escape.

About seven elapsed seconds later, with a fist pump of acknowledgment from the adjudicator (Pwn2Own is exciting for everyone, not just the hackers), and with an unsurprisingly happy smile from Manfred Paul, now $100,000 better off, the clock stopped, having just flipped over to show 29’52”.

If Win32k Lockdown was supposed to stop the Pwn2Own attack, it didn’t, although we don’t doubt that the new sandbox protection will make plenty of future exploits harder to find and less reliable to use.

To claim a Pwn2Own prize, the deal is that you have to “show your working”, in complete explanatory detail, to the maker of the system you just cracked, and give them first dibs at fixing it.

All proper bug bounties work this way, of course, but Pwn2Own isn’t just about spotting possible bugs and calling them in with a crash log, it’s about researching and writing up the bug and its dangers with careful and repeatable details, up to and including a working exploit.

Well done to everyone involved

Well, that seven-second spectacular pwnage happened on Wednesday 2022-05-18.

And on Friday 2022-05-20, about an hour before midnight UK time, Firefox popped up to tell us, “An update is available to 100.0.2”.

Here are the associated security notes, from Mozilla Security Advisory 2022-19:

* CVE-2022-1802: Prototype pollution in Top-Level Await implementation.

   Reporter: Manfred Paul via Trend Micro's Zero Day Initiative
   Impact:   Critical

   Description: If an attacker was able to corrupt the methods 
   of an Array object in JavaScript via prototype pollution, 
   they could have achieved execution of attacker-controlled 
   JavaScript code in a privileged context.


* CVE-2022-1529: Untrusted input used in JavaScript object 
                 indexing, leading to prototype pollution.

   Reporter: Manfred Paul via Trend Micro's Zero Day Initiative
   Impact:   Critical

   Description: An attacker could have sent a message to the 
   parent process where the contents were used to double-index 
   into a JavaScript object, leading to prototype pollution and 
   ultimately attacker-controlled JavaScript executing in the 
   privileged parent process.

What to do?

We’ve patched already – how about you?

For the fourth time in the past week, we’re going to say: Patch early, patch often.

With a response time like this, it would be rude not to!

Oh, and a vey big “well done and thanks” to everyone at every stage of this bug finding-and-fixing process.


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