rust openssl ssl::select_next_proto use after free

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.

rust-openssl is a set of OpenSSL bindings for the Rust programming language. In affected versions `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 `sever` 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. The crate`openssl` version 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. Users are advised to upgrade. 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.

Source published

3 Feb 2025 17:57:39 UTC

Source modified

12 Feb 2025 20:51:24 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 4.0 · 6.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N

rust-openssl is a set of OpenSSL bindings for the Rust programming language. In affected versions `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 `sever` 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. The crate`openssl` version 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. Users are advised to upgrade. 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.

Source published

Feb 3, 2025, 5:57:39 PM (timezone not stated)

Source modified

Feb 12, 2025, 8:51:24 PM (timezone not stated)

Observed here

9 Nov 2026 02:15:36 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 4.0 · 6.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N

rust-openssl is a set of OpenSSL bindings for the Rust programming language. In affected versions `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 `sever` 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. The crate`openssl` version 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. Users are advised to upgrade. 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.

Source published

3 Feb 2025 18:15:43 UTC

Source modified

17 Jun 2026 08:59:48 UTC

Observed here

25 Oct 2026 01:17:35 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 6.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

### 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. ### Patches `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. ### 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: ```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) }); ``` ### References https://github.com/sfackler/rust-openssl/pull/2360

Source published

3 Feb 2025 17:56:46 UTC

Source modified

10 Sep 2026 03:50:06 UTC

Observed here

24 Oct 2026 13:19:54 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N

Publisher rating · MODERATE

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) }); ```

Source published

2 Feb 2025 12:00:00 UTC

Source modified

12 Oct 2026 18:00:12 UTC

Observed here

24 Oct 2026 13:19:54 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.