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

GHSA-rc3f-4j82-cmrg

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (rustls-ffi 0.15.7), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • crates.io rustls-ffi

    Affected
    >= 0.12.0, < 0.15.7
    Fixed in
    0.15.7

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
not scored
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

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.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from osv record RUSTSEC-2026-0413

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: GHSA-rc3f-4j82-cmrg

Advisory: Use-after-free of caller-owned server name in client connection constructors
IDs: GHSA-rc3f-4j82-cmrg
Record: https://patchnext.com/advisories/rustsec-2026-0413 (revision 1, source checked 28 Oct 2026, 06:30 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: rustls-ffi 0.15.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io rustls-ffi: affected >= 0.12.0, < 0.15.7; fixed in 0.15.7

## Suggested inspection (read-only)
- crates.io rustls-ffi: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on rustls-ffi.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/RUSTSEC-2026-0413 (OSV record RUSTSEC-2026-0413 lists affected ranges: crates.io rustls-ffi >=0.12.0 <0.15.7 (fixed))

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