A bug in the SmallVec::insert_many method caused it to allocate a buffer that was smaller than needed. It then wrote past the end of the buffer, causing a buffer overflow and memory corruption on the heap.

This bug was only triggered if the iterator passed to insert_many yielded more items than the lower bound returned from its size_hint method.

The flaw was corrected in smallvec 0.6.14 and 1.6.1, by ensuring that additional space is always reserved for each item inserted. The fix also simplified the implementation of insert_many to use less unsafe code, so it is easier to verify its correctness.

Thank you to Yechan Bae (@Qwaz) and the Rust group at Georgia Tech’s SSLab for finding and reporting this bug.

On Windows, configuring a named pipe server with pipe_mode will force ServerOptions::reject_remote_clients as false.

This drops any intended explicit configuration for the reject_remote_clients that may have been set as true previously.

The default setting of reject_remote_clients is normally true meaning the default is also overridden as false.

Workarounds

Ensure that pipe_mode is set first after initializing a ServerOptions. For example:

let mut opts = ServerOptions::new();
opts.pipe_mode(PipeMode::Message);
opts.reject_remote_clients(true);

When this crate is given a pathological certificate chain to validate, it will spend CPU time exponential with the number of candidate certificates at each step of path building.

Both TLS clients and TLS servers that accept client certificate are affected.

We now give each path building operation a budget of 100 signature verifications.

The original webpki crate is also affected.

This was previously reported in the original crate https://github.com/briansmith/webpki/issues/69 and re-reported to us recently by Luke Malinowski.

An attacker can send a flood of CONTINUATION frames, causing h2 to process them indefinitely. This results in an increase in CPU usage.

Tokio task budget helps prevent this from a complete denial-of-service, as the server can still respond to legitimate requests, albeit with increased latency.

More details at "https://seanmonstar.com/blog/hyper-http2-continuation-flood/.

Patches available for 0.4.x and 0.3.x versions.

If a close_notify alert is received during a handshake, complete_io does not terminate.

Callers which do not call complete_io are not affected.

rustls-tokio and rustls-ffi do not call complete_io and are not affected.

rustls::Stream and rustls::StreamOwned types use complete_io and are affected.

Previously, MemBio::get_buf called slice::from_raw_parts with a null-pointer, which violates the functions invariants, leading to undefined behavior. In debug builds this would produce an assertion failure. This is now fixed.