Two vulnerabilities have been reported in scponly, which can be exploited by malicious, local users to gain escalated privileges, or by malicious users to bypass certain security restrictions.
1) A design error in "scponlyc" allows it to be used with arbitrary chroot directories that local users create in their home directories. This can be exploited by malicious users to gain escalated privileges by creating a hardlink to a setuid root binary in their own chroot directory, configuring LD_PRELOAD to overload a call to setuid with a malicious function, and then using "scponlyc" with the malicious chroot directory.
Successful exploitation allows local privilege escalation but requires that the chrooted setuid "scponlyc" binary is installed, a user executable setuid binary exists on the same file system mount as the user's home directory, and the OS supports LD_PRELOAD.
2) An error exists in the validation of user supplied command line. This can be exploited to supply additional command line arguments to rsync or scp, potentially bypassing the restricted shell and allowing the execution of arbitrary programs.
Successful exploitation requires that scp and rsync compatibility is enabled.
The vulnerabilities have been reported in version 4.1 and prior.
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Subject: scponly Privilege Escalation and Security Bypass Vulnerabilities
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