vulnerability / NVI-00018616 / Revision 1
unbounded-spsc: Sender::send pointer-as-value transmute causes OOB read and fake-Arc drop under TX/RX race
GitHub lists this reviewed advisory for unbounded-spsc. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
5.8 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
unbounded-spsc
source listed<= 0.2.0
## Summary `Sender::send` in `src/lib.rs` contains an `unsafe` block in the `DISCONNECTED` arm that transmutes a **raw pointer** (`*mut Producer`) into the bytes of a **value-level** `Consumer`. The author's intent, visible in the surrounding comment at lines 386-390, was a value transmute. The shipped code is one level of indirection off. The resulting `Consumer` has its internal `Arc::ptr` set to the address of the `producer` field on the `Sender`, not the real `ArcInner>`. Every subsequent `consumer.try_pop()` walks `Buffer` fields at offsets that lie inside the `Sender` struct (over `send_new`, `inner`) and adjacent memory, an out-of-bounds read. When the fake `Consumer` is dropped at the end of the `unsafe` block, its `Drop` calls `Arc::drop_in_place` on a non-`ArcInner` address: it decrements bytes that the type system treats as `strong_count: AtomicUsize` but that are actually the real `Arc::ptr` value of the `Sender`, and at zero count it calls `dealloc(Layout::for_value(...))` on an address the allocator never returned. Reachable from 100% safe Rust through the canonical channel pattern: a `tx.send(msg)` that races with `rx.drop()`. This is c
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-6m57-8r3p-pqx6 ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.