# GHSA-9763-4f94-gfch: CIRCL's Kyber: timing side-channel (kyberslash2)

> An attacker can potentially recover secret keys by timing decapsulation of forged ciphertexts in the Go Kyber 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:** Yes
- **Published:** 8 Jan 2024
- **Also known as:** GO-2024-2453

## What is GHSA-9763-4f94-gfch?

GHSA-9763-4f94-gfch is a vulnerability in github.com/cloudflare/circl, published on 8 Jan 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

### Impact
On some platforms, when an attacker can time decapsulation of Kyber on forged cipher texts, they could possibly learn (parts of) the secret key.

Does not apply to ephemeral usage, such as when used in the regular way in TLS.

### Patches
Patched in 1.3.7.

### References
- [kyberslash.cr.yp.to](https://kyberslash.cr.yp.to/)

## Which versions are affected by GHSA-9763-4f94-gfch?

3 open source packages ship an affected version, including github.com/cloudflare/circl.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/cloudflare/circl` | Go | All versions | 1.3.7 |
| `github.com/cloudflare/circl` | Go | All versions | 1.3.7 |
| `github.com/cloudflare/circl` | Go | All versions | 1.3.7 |

## How do I fix GHSA-9763-4f94-gfch?

Upgrade github.com/cloudflare/circl to 1.3.7 or later.

## Is GHSA-9763-4f94-gfch being exploited?

There is no known exploitation of GHSA-9763-4f94-gfch in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-9763-4f94-gfch and fix it if it is affected.

What it is: GHSA-9763-4f94-gfch is a vulnerability in github.com/cloudflare/circl, published on 8 Jan 2024. 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-9763-4f94-gfch in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/cloudflare/circl (Go): affected all versions; fixed in 1.3.7
- github.com/cloudflare/circl (Go): affected all versions; fixed in 1.3.7
- github.com/cloudflare/circl (Go): affected all versions; fixed in 1.3.7

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-9763-4f94-gfch/ (Markdown: https://insights.sbomify.com/GHSA-9763-4f94-gfch/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-9763-4f94-gfch

---
From sbomify Insights: https://insights.sbomify.com/GHSA-9763-4f94-gfch/
Summaries are generated and may contain mistakes; the official description above is the record.