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.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
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 The capture-replay claim (CWE-294) is withdrawn: the challenge is regenerated per connection (challenge = Config::get_auto_password(6)), so a captured proof is not replayable against the legitimate server.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
Which versions are affected by CVE-2026-30789?
It affects 1 product.
Products include 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 Misconfiguration in n/a
- CVE-2026-30793 RustDesk Flutter URI Handler Sets Permanent Password Without Privilege Check or User Confirmation
- CVE-2026-30797 RustDesk rustdesk://config/ URI Silently Re-homes Client to Attacker-Controlled Server
- CVE-2026-30791 RustDesk Client Accepts Pseudo-Encrypted Config Strings Without Cryptographic Validation
- CVE-2026-30795 RustDesk HTTP Client Silently Accepts Invalid TLS Certificates After Handshake Failure
Sources
Also known as GHSA-9qf7-q6gx-q652.