# RUSTSEC-2026-0239: Streaming AEAD does not authenticate stream structure


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 9 Aug 2026
- **Also known as:** GHSA-8cwp-4826-jg9f

## What is RUSTSEC-2026-0239?

RUSTSEC-2026-0239 is a vulnerability in dcrypt-symmetric, published on 9 Aug 2026. 

### Official description

In all published versions of `dcrypt-symmetric` before 2.0.0, version-1 GCM and
ChaCha20-Poly1305 streams used unauthenticated terminator, counter, and length
fields. Decryptors trusted transmitted counters, allocated from unbounded
lengths, and discarded plaintext that did not fit a caller's single read
buffer. An attacker could obtain successful truncated EOF, omit, replay, or
reorder frames within a stream, or request an allocation approaching 4 GiB.

Version 2.0.0 introduces the `DCRSTRM2` format, which authenticates its version,
algorithm, random stream identifier, base nonce, strict sequence, bounded
lengths, final flag, and caller AAD. It enforces authenticated finality and
physical EOF, bounds frames to 16 KiB before allocation, retains partial-read
plaintext, and rejects legacy version-1 input. Existing version-1 ciphertext
cannot retrospectively prove completeness or ordering and must be migrated only
through an application-specific, explicitly trusted process.

## Which versions are affected by RUSTSEC-2026-0239?

1 open source package ship an affected version, including dcrypt-symmetric.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `dcrypt-symmetric` | crates.io | From 0.0.0-0 | 2.0.0 |

## How do I fix RUSTSEC-2026-0239?

Upgrade dcrypt-symmetric to 2.0.0 or later.

## Is RUSTSEC-2026-0239 being exploited?

There is no known exploitation of RUSTSEC-2026-0239 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for RUSTSEC-2026-0239 and fix it if it is affected.

What it is: RUSTSEC-2026-0239 is a vulnerability in dcrypt-symmetric, published on 9 Aug 2026. 
Exploitation: There is no known exploitation of RUSTSEC-2026-0239 in the wild and no public exploit code.

Affected packages and fixed versions:
- dcrypt-symmetric (crates.io): affected from 0.0.0-0; fixed in 2.0.0

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-2026-0239/ (Markdown: https://insights.sbomify.com/RUSTSEC-2026-0239/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/RUSTSEC-2026-0239

---
From sbomify Insights: https://insights.sbomify.com/RUSTSEC-2026-0239/
Summaries are generated and may contain mistakes; the official description above is the record.