# RUSTSEC-2026-0391: Data from an abandoned stream leaks into the next stream on a reused context


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 16 Oct 2026

## What is RUSTSEC-2026-0391?

RUSTSEC-2026-0391 is a vulnerability in zstd, published on 16 Oct 2026. 

### Official description

The `with_context` constructors of the stream encoders and decoders used the
borrowed context as it was. When a stream was abandoned on a context, for
example an encoder dropped before `finish()` after an error, whatever it
left there was carried into the next stream: the input buffered by the
previous encoder (up to 128 KiB, or all of it with `zstdmt`) became the
start of the next frame, and a decoder returned undelivered output of the
previous stream.

An application reusing one context for data that must stay separate, such
as different users' requests, could disclose one user's plaintext to
another. Whoever supplies the data can cause the abandonment with invalid
input.

The flaw was corrected by resetting the context's session in
`with_context`.

## Which versions are affected by RUSTSEC-2026-0391?

1 open source package ship an affected version, including zstd.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `zstd` | crates.io | From 0.13.2 | 0.14.3 |

## How do I fix RUSTSEC-2026-0391?

Upgrade zstd to 0.14.3 or later.

## Is RUSTSEC-2026-0391 being exploited?

There is no known exploitation of RUSTSEC-2026-0391 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for RUSTSEC-2026-0391 and fix it if it is affected.

What it is: RUSTSEC-2026-0391 is a vulnerability in zstd, published on 16 Oct 2026. 
Exploitation: There is no known exploitation of RUSTSEC-2026-0391 in the wild and no public exploit code.

Affected packages and fixed versions:
- zstd (crates.io): affected from 0.13.2; fixed in 0.14.3

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-2026-0391/ (Markdown: https://insights.sbomify.com/RUSTSEC-2026-0391/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/RUSTSEC-2026-0391

---
From sbomify Insights: https://insights.sbomify.com/RUSTSEC-2026-0391/
Summaries are generated and may contain mistakes; the official description above is the record.