EUVD-2026-159354

fkie_cve-2024-43410

Russh is a Rust SSH client & server library. Allocating an untrusted amount of memory allows any unauthenticated user to OOM a russh server. An SSH packet consists of a 4-byte big-endian length, followed by a byte stream of this length. After parsing and potentially decrypting the 4-byte length, russh allocates enough memory for this bytestream, as a performance optimization to avoid reallocations later. But this length is entirely untrusted and can be set to any value by the client, causing this much memory to be allocated, which will cause the process to OOM within a few such requests. This vulnerability is fixed in 0.44.1.

GHSA-vgvv-x7xg-6cqg — Russh has an OOM Denial of Service due to allocation of untrusted amount

Affected: crates.io: russh

### Summary

Allocating an untrusted amount of memory allows any unauthenticated user to OOM a russh server.

### Details

An SSH packet consists of a 4-byte big-endian length, followed by a byte stream of this length. After parsing and potentially decrypting the 4-byte length, russh allocates enough memory for this bytestream, as a performance optimization to avoid reallocations later.

https://github.com/Eugeny/russh/blob/4eaa080e7532662023f75e8fff45b743fe607f8c/russh/src/cipher/mod.rs#L254

But this length is entirely untrusted and can be set to any value by the client, causing this much memory to be allocated, which will cause the process to OOM within a few such requests.

RFC 4253 contains an explicit section on packet length limits: https://datatracker.ietf.org/doc/html/rfc4253#section-6.1

> However, implementations SHOULD check that the packet length is reasonable in order for the implementation to avoid denial of service and/or buffer overflow attacks.

### PoC

Running the `echoserver` example on port 2222 (`cd russh && cargo run --release --example echoserver`), the provided Rust program can be executed against this echoserver and will cause it to OOM within a few tries.

<details> <summary>Rust code to run against the echo server</summary>

`Cargo.toml` ```toml [package] name = "poc" version = "0.1.0" edition = "2021"

[dependencies] hex-literal = "=0.4.1" ```

`main.rs` ```rust use std::time::Duration; use std::{error::Error, net::SocketAddr};

use std::{ i…

Most recent entries from all

EUVD-2026-159354

fkie_cve-2024-43410

GHSA-vgvv-x7xg-6cqg — Russh has an OOM Denial of Service due to allocation of untrusted amount