#VU51962 UNIX symbolic link following in umoci - CVE-2021-29136

Vulnerability identifier: #VU51962

Vulnerability risk: Medium

CVSSv4.0: 4.8 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-29136

CWE-ID: CWE-61

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
umoci
Other software / Other software solutions

Vendor: umo.ci

Description

The vulnerability allows a remote attacker to compromise the affected system.

The vulnerability exists due to a symlink following issue when processing crafted images. A remote attacker can create a specially crafted image with symbolic link to a critical file on the system and overwrite it, when "umoci unpack" or "umoci raw unpack" is used.

Successful exploitation of this vulnerability may result in privilege escalation.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

umoci: 0.4.0 - 0.4.6

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External links
https://www.openwall.com/lists/oss-security/2021/04/06/2
https://github.com/opencontainers/umoci/commit/d9efc31daf2206f7d3fdb839863cf7a576a2eb57
https://github.com/opencontainers/umoci/security/advisories/GHSA-9m95-8hx6-7p9v

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.