Ubuntu update for snapd

Published: 2022-02-24 | Updated: 2023-07-10

Risk	Low
Patch available	YES
Number of vulnerabilities	4
CVE-ID	CVE-2021-3155 CVE-2021-4120 CVE-2021-44730 CVE-2021-44731
CWE-ID	CWE-276 CWE-20 CWE-62 CWE-362
Exploitation vector	Local
Public exploit	Public exploit code for vulnerability #4 is available.
Vulnerable software	Ubuntu Operating systems & Components / Operating system snapd (Ubuntu package) Operating systems & Components / Operating system package or component snap-confine (Ubuntu package) Operating systems & Components / Operating system package or component
Vendor	Canonical Ltd.

Security Bulletin

This security bulletin contains information about 4 vulnerabilities.

1) Incorrect default permissions

EUVDB-ID: #VU63646

Risk: Low

CVSSv4.0: 1.1 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2021-3155

CWE-ID: CWE-276 - Incorrect Default Permissions

Exploit availability: No

Description

The vulnerability allows a local user to gain access to sensitive information.

The vulnerability exists due to snapd creates "~/snap" directories in user home directories without specifying owner-only permissions. A local user can gain access to potentially sensitive information.

Mitigation

Update the affected package snapd to the latest version.

Vulnerable software versions

Ubuntu: 14.04 - 21.10

snapd (Ubuntu package): before 2.54.3+18.04.2ubuntu0.2

snap-confine (Ubuntu package): before 2.54.3+18.04.2ubuntu0.2

CPE2.3

External links

https://ubuntu.com/security/notices/USN-5292-4

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.

2) Input validation error

EUVDB-ID: #VU60744

Risk: Low

CVSSv4.0: 5.9 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2021-4120

CWE-ID: CWE-20 - Improper input validation

Exploit availability: No

Description

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to insufficient validation of snap content interface and layout paths. A local user can inject arbitrary AppArmor policy rules via malformed content interface and layout declarations and execute arbitrary code with elevated privileges.

Mitigation

Update the affected package snapd to the latest version.

Vulnerable software versions

Ubuntu: 14.04 - 21.10

snapd (Ubuntu package): before 2.54.3+18.04.2ubuntu0.2

snap-confine (Ubuntu package): before 2.54.3+18.04.2ubuntu0.2

CPE2.3

External links

https://ubuntu.com/security/notices/USN-5292-4

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.

3) UNIX hardlink following

EUVDB-ID: #VU60742

Risk: Low

CVSSv4.0: 5.9 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2021-44730

CWE-ID: CWE-62 - UNIX Hard Link

Exploit availability: No

Description

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to a hardlink following issue within the the snap-confine binary. A local user can create a hardlink to system binaries and execute them with elevated privileges.

Mitigation

Update the affected package snapd to the latest version.

Vulnerable software versions

Ubuntu: 14.04 - 21.10

snapd (Ubuntu package): before 2.54.3+18.04.2ubuntu0.2

snap-confine (Ubuntu package): before 2.54.3+18.04.2ubuntu0.2

CPE2.3

External links

https://ubuntu.com/security/notices/USN-5292-4

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.

4) Race condition

EUVDB-ID: #VU60743

Risk: Low

CVSSv4.0: 7.1 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P/U:Clear]

CVE-ID: CVE-2021-44731

CWE-ID: CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

Exploit availability: Yes

Description

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to a race condition in the snap-confine binary when preparing a private mount namespace for a snap.. A local user can bind-mount their own contents inside the snap's private mount namespace and execute arbitrary code with root privileges.

Mitigation

Update the affected package snapd to the latest version.

Vulnerable software versions

Ubuntu: 14.04 - 21.10

snapd (Ubuntu package): before 2.54.3+18.04.2ubuntu0.2

snap-confine (Ubuntu package): before 2.54.3+18.04.2ubuntu0.2

CPE2.3

External links

https://ubuntu.com/security/notices/USN-5292-4

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.