A wrong assumption made when handling ECMAScript's AsyncGenerator operations can cause an uncaught exception on certain scripts.
Details
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.
Patches
Version 0.19.0 is patched to correctly handle this case.
Workarounds
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.
References
References
ctcpip Coordinator
arai-a Reporter
jedel1043 Remediation developer
jasonwilliams Remediation reviewer
nekevss Remediation reviewer
A wrong assumption made when handling ECMAScript's
AsyncGeneratoroperations can cause an uncaught exception on certain scripts.Details
Boa's implementation of
AsyncGeneratormakes the assumption that the state of anAsyncGeneratorobject cannot change while resolving a promise created by methods ofAsyncGeneratorsuch 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
thenproperty, 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.Patches
Version 0.19.0 is patched to correctly handle this case.
Workarounds
Users unable to upgrade to the patched version would want to use
std::panic::catch_unwindto ensure any exceptions caused by the engine don't impact the availability of the main application.References
References