Summary
rust-openssl ssl::selectnextproto use after free
Workarounds
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:
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:
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:
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)
});
References
Impact
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.
Memory is accessed after it has been freed, leading to undefined behavior in native code. Typical impact: memory corruption, crash, or potential code execution.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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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.
Frequently Asked Questions
- What is CVE-2025-24898? CVE-2025-24898 is a medium-severity use after free vulnerability in openssl (rust), affecting versions >= 0.10.0, < 0.10.70. It is fixed in 0.10.70. Memory is accessed after it has been freed, leading to undefined behavior in native code.
- Which versions of openssl are affected by CVE-2025-24898? openssl (rust) versions >= 0.10.0, < 0.10.70 is affected.
- Is there a fix for CVE-2025-24898? Yes. CVE-2025-24898 is fixed in 0.10.70. Upgrade to this version or later.
- Is CVE-2025-24898 exploitable, and should I be worried? Whether CVE-2025-24898 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-24898 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2025-24898? Upgrade
opensslto 0.10.70 or later.