Vulnerability identifier: #VU16782

Vulnerability 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

Exploitation vector: Local

Exploit availability: No

Vulnerable software:
Tar
Client/Desktop applications / Software for archiving

Vendor: GNU

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

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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

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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.

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.