Denial of service in GNU Tar

1) Infinite loop

EUVDB-ID: #VU16782

Risk: Low

CVSSv3.1: 5 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2018-20482

CWE-ID: CWE-835 - Loop with Unreachable Exit Condition ('Infinite Loop')

Exploit availability: No

Description

The vulnerability allows a local attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to the application mishandles file shrinkage during read access when --sparse is used. A local attacker can trigger infinite read loop in sparse_dump_region in sparse.c by modifying a file that is supposed to be archived by a different user's process (e.g., a system backup running as root) and cause denial of service conditions.

Mitigation

Install update from vendor's website.

Vulnerable software versions

Tar: 1.13 - 1.30

External links

http://lists.gnu.org/archive/html/bug-tar/2018-12/msg00023.html
http://git.savannah.gnu.org/cgit/tar.git/commit/?id=c15c42ccd1e2377945fd0414eca1a49294bff454

Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

How the attacker can exploit this vulnerability?

The attacker would have to trick the victim to open a a specially crafted archive.

The attacker would have to login to the system and perform certain actions in order to exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.