Ubuntu update for zsh
| Risk | High |
| Patch available | YES |
| Number of vulnerabilities | 2 |
| CVE-ID | CVE-2019-20044 CVE-2021-45444 |
| CWE-ID | CWE-273 CWE-78 |
| Exploitation vector | Network |
| Public exploit | Public exploit code for vulnerability #1 is available. |
| Vulnerable software |
Ubuntu Operating systems & Components / Operating system zsh (Ubuntu package) Operating systems & Components / Operating system package or component zsh-static (Ubuntu package) Operating systems & Components / Operating system package or component |
| Vendor | Canonical Ltd. |
Security Bulletin
This security bulletin contains information about 2 vulnerabilities.
1) Improper Check for Dropped Privileges
EUVDB-ID: #VU26210
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-2019-20044
CWE-ID:
CWE-273 - Improper Check for Dropped Privileges
Exploit availability: Yes
DescriptionThe vulnerability allows a local user to escalate privileges on the system.
The vulnerability exists due to Zsh fails to overwrite the saved uid, so the original privileges, dropped by the --no-PRIVILEGED option, can be restored by
executing MODULE_PATH=/dir/with/module zmodload with a module that calls
setuid(). A local user can execute arbitrary commands on the system with elevated privileges.
Update the affected package zsh to the latest version.
Vulnerable software versionsUbuntu: 16.04 - 21.10
zsh (Ubuntu package): before UA Infra or UA Desktop
zsh-static (Ubuntu package): before UA Infra or UA Desktop
CPE2.3- cpe:2.3:o:canonical:ubuntu:16.04:*:*:*:*:*:*:*
- cpe:2.3:o:canonical:ubuntu:18.04:*:*:*:*:*:*:*
- cpe:2.3:o:canonical:ubuntu:20.04:*:*:*:*:*:*:*
- cpe:2.3:o:canonical:ubuntu:21.10:*:*:*:*:*:*:*
- cpe:2.3:a:canonical:zsh_ubuntu_package:*:*:*:*:*:ubuntu:*:*
- cpe:2.3:a:canonical:zsh-static_ubuntu_package:*:*:*:*:*:ubuntu:*:*
https://ubuntu.com/security/notices/USN-5325-1
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.
2) OS Command Injection
EUVDB-ID: #VU60674
Risk: High
CVSSv4.0: 5.7 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber]
CVE-ID: CVE-2021-45444
CWE-ID:
CWE-78 - Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
Exploit availability: No
DescriptionThe vulnerability allows a remote attacker to execute arbitrary shell commands on the target system.
The vulnerability exists due to recursive PROMPT_SUBST expansion when processing malicious output. A remote attacker with ability to control the output can inject and execute arbitrary commands on the system with privileges on the current user.
Mitigation
Update the affected package zsh to the latest version.
Vulnerable software versionsUbuntu: 16.04 - 21.10
zsh (Ubuntu package): before UA Infra or UA Desktop
zsh-static (Ubuntu package): before UA Infra or UA Desktop
CPE2.3- cpe:2.3:o:canonical:ubuntu:16.04:*:*:*:*:*:*:*
- cpe:2.3:o:canonical:ubuntu:18.04:*:*:*:*:*:*:*
- cpe:2.3:o:canonical:ubuntu:20.04:*:*:*:*:*:*:*
- cpe:2.3:o:canonical:ubuntu:21.10:*:*:*:*:*:*:*
- cpe:2.3:a:canonical:zsh_ubuntu_package:*:*:*:*:*:ubuntu:*:*
- cpe:2.3:a:canonical:zsh-static_ubuntu_package:*:*:*:*:*:ubuntu:*:*
https://ubuntu.com/security/notices/USN-5325-1
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.
