A use-after-free issue could be triggered remotely in the SFTP component of PSFTPd 10.0.4 Build 729. This issue could be triggered prior to authentication. The PSFTPd server did not automatically restart, which enabled attackers to perform a very effective DoS attack against this service. By sending a crafted SSH identification / version string to the server, a NULL pointer dereference could be caused, apparently because of a race condition in the window message handling, performing the cleanup for invalid connections. This incorrect cleanup code has a use-after-free.
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
| Link | Tags |
|---|---|
| http://packetstormsecurity.com/files/144972/PSFTPd-Windows-FTP-Server-10.0.4-Build-729-Use-After-Free-Log-Injection.html | vdb entry third party advisory |
| http://www.securityfocus.com/archive/1/541518/100/0/threaded | mailing list |
| https://www.x41-dsec.de/lab/advisories/x41-2017-006-psftpd/ | third party advisory |
| https://www.exploit-db.com/exploits/43144/ | exploit vdb entry third party advisory |