Impact

Unix-like operating systems may segfault due to dereferencing a dangling pointer in specific circumstances. This requires an environment variable to be set in a different thread than the affected functions. This may occur without the user's knowledge, notably in a third-party library.

Workarounds

No workarounds are known.

References

• time-rs/time#293

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);

Due to insufficient checking of input data, decoding certain data sequences can lead to Decoder::decode panicking rather than returning an error.

Example code that triggers this vulnerability looks like this:

use hpack::Decoder;

pub fn main() {
  let input = &[0x3f];
  let mut decoder = Decoder::new();
  let _ = decoder.decode(input);
}

hpack is unmaintained. A crate with the panics fixed has been published as hpack-patched.

Also consider using loona-hpack or httlib-huffman as an alternative.

Version 0.3.1 of fluke-hpack still reproduces the panic described in this advisory.

A bug introduced in rustls 0.23.13 leads to a panic if the received TLS ClientHello is fragmented. Only servers that use rustls::server::Acceptor::accept() are affected.

Servers that use tokio-rustls's LazyConfigAcceptor API are affected.

Servers that use tokio-rustls's TlsAcceptor API are not affected.

Servers that use rustls-ffi's rustls_acceptor_accept API are affected.

In the unique reclaim path of BytesMut::reserve, the condition

if v_capacity >= new_cap + offset

uses an unchecked addition. When new_cap + offset overflows usize in release builds, this condition may incorrectly pass, causing self.cap to be set to a value that exceeds the actual allocated capacity. Subsequent APIs such as spare_capacity_mut() then trust this corrupted cap value and may create out-of-bounds slices, leading to UB.

This behavior is observable in release builds (integer overflow wraps), whereas debug builds panic due to overflow checks.

PoC

use bytes::*;

fn main() {
    let mut a = BytesMut::from(&b"hello world"[..]);
    let mut b = a.split_off(5);

    // Ensure b becomes the unique owner of the backing storage
    drop(a);

    // Trigger overflow in new_cap + offset inside reserve
    b.reserve(usize::MAX - 6);

    // This call relies on the corrupted cap and may cause UB & HBO
    b.put_u8(b'h');
}

Workarounds

Users of BytesMut::reserve are only affected if integer overflow checks are configured to wrap. When integer overflow is configured to panic, this issue does not apply.