# RUSTSEC-2026-0252: Panic-safety unsoundness in `SplitVec::extend_from_slice` (uninitialized read)

> A panic during cloning in SplitVec::extend_from_slice leaves uninitialized memory accessible, allowing attackers to read garbage data or cause crashes.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Not stated
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Aug 2026

## What is RUSTSEC-2026-0252?

RUSTSEC-2026-0252 is a memory corruption vulnerability in orx-split-vec, published on 11 Aug 2026. 

### Official description

`SplitVec::extend_from_slice` increments the logical length `self.len` before cloning the incoming elements into the reserved slots. If an element's `Clone` panics mid-fill, unwinding leaves `self.len` counting slots that were never initialized. A later safe read (`get`, indexing, `iter`) then reads one of those uninitialized slots.

This is reachable from safe Rust — a read of uninitialized memory (CWE-908). It is not a double-free: `SplitVec` has no manual `Drop` and its elements live in a standard `Vec`, so the defect is a read, not a free.

## Impact

A safe read after the panic returns a value built from uninitialized bytes. For a heap-owning element type such as `String`, the resulting value has garbage length/pointer fields.

Confirmed under Miri. AddressSanitizer stays silent for this class, since the uninitialized bytes are consumed as a non-dereferenced field rather than an invalid load or free.

## Fix

Fixed in `orx-split-vec` 4.0.0, which no longer commits the length before the elements are cloned.

## Which versions are affected by RUSTSEC-2026-0252?

1 open source package ship an affected version, including orx-split-vec.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `orx-split-vec` | crates.io | From 0.0.0-0 | 4.0.0 |

## How do I fix RUSTSEC-2026-0252?

Upgrade orx-split-vec to 4.0.0 or later.

## Is RUSTSEC-2026-0252 being exploited?

There is no known exploitation of RUSTSEC-2026-0252 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for RUSTSEC-2026-0252 and fix it if it is affected.

What it is: RUSTSEC-2026-0252 is a memory corruption vulnerability in orx-split-vec, published on 11 Aug 2026. 
Exploitation: There is no known exploitation of RUSTSEC-2026-0252 in the wild and no public exploit code.

Affected packages and fixed versions:
- orx-split-vec (crates.io): affected from 0.0.0-0; fixed in 4.0.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/RUSTSEC-2026-0252/ (Markdown: https://insights.sbomify.com/RUSTSEC-2026-0252/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/RUSTSEC-2026-0252

---
From sbomify Insights: https://insights.sbomify.com/RUSTSEC-2026-0252/
Summaries are generated and may contain mistakes; the official description above is the record.