Infinite loop in tar (Alpine package)

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 (Alpine package): 1.22-r0 - 1.30-r1

External links

http://git.alpinelinux.org/aports/commit/?id=aafb402f4f09442d1762bef4429f4a6018d2569b
http://git.alpinelinux.org/aports/commit/?id=0119db774c8cbd96f7d4d966f9fa9c2f788f223a
http://git.alpinelinux.org/aports/commit/?id=25c0433d9b2f5d1714a20c53a424eb8726bc00e6
http://git.alpinelinux.org/aports/commit/?id=85863f590a9cdcd1a2e5bcf772ad49ca4c5d3c37
http://git.alpinelinux.org/aports/commit/?id=e37604c4a87ded07554695c98e2fd64157014fc7

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.