Description
Matt Johnston Dropbear SSH server 0.47 and earlier, as used in embedded Linux devices and on general-purpose operating systems, allows remote attackers to cause a denial of service (connection slot exhaustion) via a large number of connection attempts that exceeds the MAX_UNAUTH_CLIENTS defined value of 30.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | dropbear | 0.48-1 | — |
| Debian 13 | dropbear | 0.48-1 | — |
| Debian 12 | dropbear | 0.48-1 | — |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
Exploit-DB 1
- Dropbear / OpenSSH Server - 'MAX_UNAUTH_CLIENTS' Denial of Service EDB-1572 · dos · Mar 10, 2006 · verified
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
References
- 20060307 Dropbear SSH server Denial of Service mailing-list
- 17024 vdb-entry
- dropbear-connection-dos(25075) vdb-entry
- 1015742 vdb-entry