---
id: CVE-2025-24898
aliases:
  - RUSTSEC-2025-0004
  - GHSA-rpmj-rpgj-qmpm
title: 'ssl::select_next_proto use after free'
summary: 'ssl::select_next_proto use after free'
severity: none
vendor: openssl
product: openssl
ecosystem: rust
affected:
  - 'openssl >= 0.0.0-0, < 0.10.70'
patched:
  - openssl 0.10.70
published: '2025-02-02'
updated: '2026-10-12'
sourceUpdated: '2026-10-12T18:00:12.406916247Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/RUSTSEC-2025-0004'
references:
  - url: 'https://crates.io/crates/openssl'
  - url: 'https://rustsec.org/advisories/RUSTSEC-2025-0004.html'
  - url: 'https://github.com/sfackler/rust-openssl/pull/2360'
  - url: 'https://github.com/sfackler/rust-openssl/pull/2360'
tags:
  - osv
  - rust
epss: 0.0068
epssPercentile: 0.51068
ingestedAt: '2026-10-13T11:45:30.176Z'
---

## Overview

In `openssl` versions before `0.10.70`, `ssl::select_next_proto` can return a slice pointing into the `server` argument's buffer but with a lifetime bound to the `client` argument. In situations where the `server` buffer's lifetime is shorter than the `client` buffer's, this can cause a use after free. This could cause the server to crash or to return arbitrary memory contents to the client.

`openssl` 0.10.70 fixes the signature of `ssl::select_next_proto` to properly constrain the output buffer's lifetime to that of both input buffers.

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. For example:

Not vulnerable - the server buffer has a `'static` lifetime:
```rust
builder.set_alpn_select_callback(|_, client_protos| {
    ssl::select_next_proto(b"\x02h2", client_protos).ok_or_else(AlpnError::NOACK)
});
```

Not vulnerable - the server buffer outlives the handshake:
```rust
let server_protos = b"\x02h2".to_vec();
builder.set_alpn_select_callback(|_, client_protos| {
    ssl::select_next_proto(&server_protos, client_protos).ok_or_else(AlpnError::NOACK)
});
```

Vulnerable - the server buffer is freed when the callback returns:
```rust
builder.set_alpn_select_callback(|_, client_protos| {
    let server_protos = b"\x02h2".to_vec();
    ssl::select_next_proto(&server_protos, client_protos).ok_or_else(AlpnError::NOACK)
});
```

## Affected packages

- `openssl >= 0.0.0-0, < 0.10.70`

## Remediation

Upgrade to a patched release:

- `openssl 0.10.70`