Use-after-free of caller-owned server name in client connection constructors

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

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.

Source published

26 Oct 2026 12:00:00 UTC

Source modified

27 Oct 2026 10:15:12 UTC

Observed here

27 Oct 2026 11:11:53 UTC

Source terms

OSV · upstream source license applies

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