# GHSA-6w86-wgwq-rgq8: neqo-qpack has iInteger overflow in qpack dynamic table indexing

> A malicious remote attacker can cause a QUIC connection to fail or enter an inconsistent state via integer overflow in the neqo-qpack library.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 4 Mar 2026

## What is GHSA-6w86-wgwq-rgq8?

GHSA-6w86-wgwq-rgq8 is a vulnerability in neqo-qpack, published on 4 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

### Summary

An unsanitized qpack index can lead to an integer overflow, panicing in debug mode, accessing the wrong or no dynamic table entry in release mode.

What does this mean for Firefox? Firefox runs Neqo in release mode. A malicious remote can cause its own QUIC connection to fail to use qpack, i.e. compression, or enter an inconsistent state. The remote can not crash Firefox, nor affect other QUIC connections. 

### Details

See fuzz report in https://github.com/mozilla/neqo/issues/3406.

### PoC
See test in pull request.

### Impact
All Firefox users. Though vulnerability likely scoped to same connection, i.e. low impact.

## Which versions are affected by GHSA-6w86-wgwq-rgq8?

2 open source packages ship an affected version, including neqo-qpack.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `neqo-qpack` | crates.io | All versions to 0.22.2 | None |
| `neqo-qpack` | crates.io | All versions to 0.22.2 | None |

## How do I fix GHSA-6w86-wgwq-rgq8?

No fix has been published for GHSA-6w86-wgwq-rgq8 yet. Limit exposure of the affected software until one is available.

## Is GHSA-6w86-wgwq-rgq8 being exploited?

There is no known exploitation of GHSA-6w86-wgwq-rgq8 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-6w86-wgwq-rgq8 and fix it if it is affected.

What it is: GHSA-6w86-wgwq-rgq8 is a vulnerability in neqo-qpack, published on 4 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of GHSA-6w86-wgwq-rgq8 in the wild and no public exploit code.

Affected packages and fixed versions:
- neqo-qpack (crates.io): affected all versions up to 0.22.2; no fix listed
- neqo-qpack (crates.io): affected all versions up to 0.22.2; no fix listed

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/GHSA-6w86-wgwq-rgq8/ (Markdown: https://insights.sbomify.com/GHSA-6w86-wgwq-rgq8/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-6w86-wgwq-rgq8

---
From sbomify Insights: https://insights.sbomify.com/GHSA-6w86-wgwq-rgq8/
Summaries are generated and may contain mistakes; the official description above is the record.