tar-fs Hardlink Tarball Extraction Arbitrary File Overwrite Vulnerability [CVE-2018-20835]

CVE Number – CVE-2018-20835

A vulnerability in tar-fs could allow a local attacker to overwrite arbitrary files on a targeted system.The vulnerability exists because the affected software improperly validates user-supplied input. An attacker could exploit this vulnerability by extracting a tarball that contains a hard link to a file on the targeted system. A successful exploit could allow the attacker to overwrite arbitrary files on the targeted system.Proof-of-concept (PoC) code that demonstrates an exploit of this vulnerability is publicly available.The vendor has confirmed the vulnerability and released software updates.

Analysis

  • To exploit this vulnerability, the attacker must have user-level access to the targeted system. This access requirement could reduce the likelihood of a successful exploit.

Safeguards

  • Administrators are advised to apply the appropriate updates.Administrators are advised to allow only trusted users to access local systems.Administrators are advised to allow only privileged users to access administration or management systems.Administrators are advised to monitor critical systems.

Vendor Announcements

Fixed Software

  • The vendor has released software updates at the following link: tar-fs releases

Duncan Newell

Duncan is a technology professional with over 20 years experience of working in various IT roles. He has a interest in cyber security, and has a wide range of other skills in radio, electronics and telecommunications.

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