Unbounded memory allocation in `thrift` binary protocol `read_bytes`

Affected versions of the `thrift` crate size a buffer directly from an attacker-controlled 4-byte length read off the wire, before reading any payload and with no upper bound, allowing a hostile peer to force a large eager allocation or an immediate abort (denial of service, CWE-400 / CWE-789). This is the Rust implementation's instance of the CVE-2020-13949 pattern, published by the Apache Thrift PMC as CVE-2026-43868. ## Details In `TBinaryInputProtocol::read_bytes` (`src/protocol/binary.rs`), the length is read as a `i32` from the transport and cast straight to `usize` to size a zeroing buffer **before** any payload is read: ```rust fn read_bytes(&mut self) -> crate::Result<Vec<u8>> { let num_bytes = self.transport.read_i32::<BigEndian>()? as usize; // length from the wire let mut buf = vec![0u8; num_bytes]; // unbounded eager allocation self.transport.read_exact(&mut buf).map(|_| buf).map_err(From::from) } ``` There is no check that `num_bytes` is non-negative or that it fits within the data actually available: - A length of `0x7FFFFFFF` forces a ~2 GiB allocation; `0x20000000` forces 512 MiB; and so on, from only a 4-byte input. - A negative length casts to a huge `usize` (up to `usize::MAX`), causing an immediate allocation failure / abort. `read_string` routes through `read_bytes`, so string fields are affected the same way. The sink is reachable from any peer sending binary-protocol data, so this is an unauthenticated, network-reachable denial of service. ## The fix From `thrift` 0.23.0 onward, `read_bytes` goes through `read_binary_len`, which rejects negative sizes and enforces `TConfiguration::max_string_size` (default 100 MiB), alongside default message, frame, and recursion limits. A separate, related gap on the non-strict message-name path was published as CVE-2026-58389 and fixed in 0.24.0; this advisory covers the `read_bytes` unbounded allocation (CVE-2026-43868), fixed in 0.23.0.

Source published

2 Nov 2026 12:00:00 UTC

Source modified

2 Nov 2026 12:10:42 UTC

Observed here

2 Nov 2026 13:57:24 UTC

Source terms

OSV · upstream source license applies

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CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H