CVE-2025-24898 - Rust-OpenSSL Use After Free Vulnerability

Rust-openssl is an essential library that provides OpenSSL bindings for the Rust programming language. The library is widely used for implementing SSL/TLS protocols and cryptographic operations in various Rust-based applications. Unfortunately, a recent vulnerability (CVE-2025-24898) was discovered in rust-openssl that can lead to use after free issues. In this article, we'll explore the severity of this vulnerability, provide recommendations on how to address it, and examine the exploit detailed in the original references.

Background

Use after free is a severe memory-related issue that occurs when a program continues to use a memory location after it has been freed. This can lead to crashes, undesirable behavior, or security vulnerabilities. In CVE-2025-24898, the issue lies within the ssl::select_next_proto function of rust-openssl.

Exploit Details

The core issue in rust-openssl is in the ssl::select_next_proto function, where it returns a slice pointing to the server argument’s buffer bound to the client argument’s lifetime. When a situation arises where the server buffer's lifetime is shorter than the client buffer's, it can cause a use after free problem. Consequently, this vulnerability can cause the server to crash or return arbitrary memory contents to the client.

Here is a code snippet illustrating the issue

fn vulnerable_select_next_proto(client: &[u8], server: &[u8]) -> Option<&[u8]> {
    ssl::select_next_proto(client, server) // Incorrect buffer's lifetime
}

Fixes and Recommendations

The crate openssl version .10.70 fixes the signature of ssl::select_next_proto to properly constrain the output buffer's lifetime to that of both input buffers. Users are advised to upgrade to this version or newer to resolve the vulnerability. Additionally, in standard usage of ssl::select_next_proto in the callback passed to SslContextBuilder::set_alpn_select_callback, code is only affected if the server buffer is constructed *within* the callback.

Original References

1. CVE-2025-24898 Vulnerability Details
2. Rust-OpenSSL Official Repository
3. OpenSSL Crate API documentation
4. Rust Programming Language

Conclusion

CVE-2025-24898 poses a significant threat to applications that use vulnerable versions of rust-openssl. By understanding the exploit details and upgrading to the latest stable version (.10.70 at the time of writing), developers can help protect their applications from potentially severe impacts such as denial of service (DoS) or the leakage of sensitive information. Always remember to stay up-to-date with the latest security advisories and updates to keep your codebase and applications safe.

Timeline

Published on: 02/03/2025 18:15:43 UTC
Last modified on: 02/11/2025 08:15:32 UTC