# CVE-2026-24785: Clatter has a PSK Validity Rule Violation issue

> Clatter library allowed PSK handshake patterns violating protocol rules, potentially enabling key reuse and weakening encryption security.

- **Severity:** High 8.0 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 Jan 2026
- **Updated:** 28 Jan 2026
- **Also known as:** GHSA-253q-9q78-63x4

## What is CVE-2026-24785?

CVE-2026-24785 is a high-severity vulnerability in jmlepisto clatter, published on 27 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Clatter is a no_std compatible, pure Rust implementation of the Noise protocol framework with post-quantum support. Versiosn prior to2.2.0 have a protocol compliance vulnerability. The library allowed post-quantum handshake patterns that violated the PSK validity rule (Noise Protocol Framework Section 9.3). This could allow PSK-derived keys to be used for encryption without proper randomization by self-chosen ephemeral randomness, weakening security guarantees and potentially allowing catastrophic key reuse. Affected default patterns include `noise_pqkk_psk0`, `noise_pqkn_psk0`, `noise_pqnk_psk0`, `noise_pqnn_psk0``, and some hybrid variants. Users of these patterns may have been using handshakes that do not meet the intended security properties. The issue is fully patched and released in Clatter v2.2.0. The fixed version includes runtime checks to detect offending handshake patterns. As a workaround, avoid using offending `*_psk0` variants of post-quantum patterns. Review custom handshake patterns carefully.

Weakness: CWE-327 (Use of a Broken or Risky Cryptographic Algorithm)

## Which versions are affected by CVE-2026-24785?

2 open source packages ship an affected version, including clatter. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `clatter` | crates.io | All versions | 2.2.0 |
| `clatter` | crates.io | All versions | 2.2.0 |

Products: Jmlepisto Clatter.

## How do I fix CVE-2026-24785?

Upgrade clatter to 2.2.0 or later.

## Is CVE-2026-24785 being exploited?

There is no known exploitation of CVE-2026-24785 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-24785 and fix it if it is affected.

What it is: CVE-2026-24785 is a high-severity vulnerability in jmlepisto clatter, published on 27 Jan 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 CVE-2026-24785 in the wild and no public exploit code.

Affected packages and fixed versions:
- clatter (crates.io): affected all versions; fixed in 2.2.0
- clatter (crates.io): affected all versions; fixed in 2.2.0

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/CVE-2026-24785/ (Markdown: https://insights.sbomify.com/CVE-2026-24785/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-24785
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-24785
- OSV: https://osv.dev/vulnerability/CVE-2026-24785

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-24785/
Summaries are generated and may contain mistakes; the official description above is the record.