CVE-2024-43367High· 8.6▾ TwilightUncaught exception when transitioning the state of `AsyncGenerator` objects from within a property getter of `then`
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 47.3 · likelihood 0.1 · exploitation 0
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Exploit-prediction probability, daily snapshots since Oct 13.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via OSV
Last analysed / modified upstream
0.6%
A wrong assumption made when handling ECMAScript's AsyncGenerator operations can cause an uncaught exception on certain scripts.
Boa's implementation of AsyncGenerator makes the assumption that the state of an AsyncGenerator object cannot change while resolving a promise created by methods of AsyncGenerator such as %AsyncGeneratorPrototype%.next, %AsyncGeneratorPrototype%.return, or %AsyncGeneratorPrototype%.throw.
However, a carefully constructed code could trigger a state transition from a getter method for the promise's then property, which causes the engine to fail an assertion of this assumption, causing an uncaught exception. This could be used to create a Denial Of Service attack in applications that run arbitrary ECMAScript code provided by an external user.
Version 0.19.0 is patched to correctly handle this case.
Users unable to upgrade to the patched version would want to use std::panic::catch_unwind to ensure any exceptions caused by the engine don't impact the availability of the main application.
boa_engine >= 0.16.0, < 0.19.0Upgrade to a patched release:
boa_engine 0.19.0