# CVE-2026-30789: RustDesk Auth Proof Uses Server-Controlled Salt/Challenge and Fast Double-SHA256, Enabling Offline Brute-Force

> Rogue servers can capture weak authentication proofs to perform offline brute-force attacks, recovering user passwords.

- **Severity:** Medium 5.7 (`CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 5 Mar 2026
- **Updated:** 22 Jun 2026
- **Also known as:** GHSA-9qf7-q6gx-q652

## What is CVE-2026-30789?

CVE-2026-30789 is a medium-severity vulnerability in rustdesk-client RustDesk Client, published on 5 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Use of Password Hash With Insufficient Computational Effort, Improper Restriction of Excessive Authentication Attempts vulnerability in rustdesk-client RustDesk Client rustdesk-client on Windows, MacOS, Linux, iOS, Android (Client login, peer authentication modules) allows Password Brute Forcing.

The authentication proof is SHA256(SHA256(password + salt) + challenge), where both the salt and the challenge are generated entirely by the server with no client-side nonce, and the hash uses no slow key-derivation function. A rogue or on-path API/relay server (see CVE-2026-30794 / CVE-2026-30797) can issue a chosen salt and challenge, capture the resulting proof, and recover the password offline. The capture-replay claim (CWE-294) is withdrawn: the challenge is regenerated per connection (challenge = Config::get_auto_password(6)), so a captured proof is not replayable against the legitimate server. The 1.4.7 OTP brute-force limiter and the existing LOGIN_FAILURES counter constrain only ONLINE attempts and do not address offline recovery.

This vulnerability is associated with program files src/client.rs and program routines handle_hash(), handle_login_from_ui() (login proof construction).

This issue affects RustDesk Client: through 1.4.8.

Weakness: CWE-916 (Use of Password Hash With Insufficient Computational Effort)

## Which versions are affected by CVE-2026-30789?

It affects 1 product.


Products: Rustdesk Rustdesk.

## How do I fix CVE-2026-30789?

No fix has been published for CVE-2026-30789 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-30789 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-30789 exists.

## Other vulnerabilities in rustdesk-client RustDesk Client

- [CVE-2024-25140](https://insights.sbomify.com/CVE-2024-25140/): Misconfiguration in n/a (critical 9.8)
- [CVE-2026-30793](https://insights.sbomify.com/CVE-2026-30793/): RustDesk Flutter URI Handler Sets Permanent Password Without Privilege Check or User Confirmation (critical 9.3)
- [CVE-2026-30797](https://insights.sbomify.com/CVE-2026-30797/): RustDesk rustdesk://config/ URI Silently Re-homes Client to Attacker-Controlled Server (critical 9.3)
- [CVE-2026-30791](https://insights.sbomify.com/CVE-2026-30791/): RustDesk Client Accepts Pseudo-Encrypted Config Strings Without Cryptographic Validation (high 8.7)
- [CVE-2026-30795](https://insights.sbomify.com/CVE-2026-30795/): RustDesk HTTP Client Silently Accepts Invalid TLS Certificates After Handshake Failure (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-30789 and fix it if it is affected.

What it is: CVE-2026-30789 is a medium-severity vulnerability in rustdesk-client RustDesk Client, published on 5 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-30789 exists.

Affected product: rustdesk-client RustDesk Client. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-30789/ (Markdown: https://insights.sbomify.com/CVE-2026-30789/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-30789
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-30789
- OSV: https://osv.dev/vulnerability/CVE-2026-30789

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-30789/
Summaries are generated and may contain mistakes; the official description above is the record.