Security Advisory 2021-01
| Summary | Local privilege escalation in Octopus Server (CVE-2021-26556) |
| Advisory Number | 2021-01 |
| Discovery Date | 01 Jan 2021 |
| Patch Release Date | 07 Mar 2021 |
| Advisory Release Date | 10 Mar 2021 |
| Product | Octopus Server |
| Operating System | Windows |
| Severity | High |
| CVE ID | CVE-2021-26556 |
Customers who have downloaded and installed any of the Octopus Server versions listed below ("Details") are affected.
Please upgrade your Octopus Server immediately to fix this vulnerability.
Customers using Octopus Cloud are not affected.
Customers who have upgraded Octopus Server to version 2020.6.4671 or higher are not affected.
Severity
Octopus Deploy has given this vulnerability a high rating. This rating was given according to the Octopus Deploy severity levels, which ranks vulnerabilities as critical, high, medium, or low severity.
This is our assessment and you should evaluate its applicability to your own environment.
Details
When Octopus Server is installed using a custom folder location, folder ACLs are not set correctly and could lead to an unprivileged user using DLL side-loading to gain privileged access.
The versions of Octopus Server affected by this vulnerability are:
-
All 0.x.x, 1.x.x, 2.x.x, 3.x.x, 4.x.x versions
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All 2018.x.x, 2019.x.x, 2020.1.x, 2020.2.x, 2020.3.x versions
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All 2020.4.x versions before 2020.4.229
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All 2020.5.x versions before 2020.5.256
This issue can be tracked here: https://github.com/OctopusDeploy/Issues/issues/6786
Fix
To address this vulnerability, we have released Octopus Server versions:
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2020.4.229
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2020.5.256
-
2020.6.4671
The latest versions of Octopus Deploy products can be downloaded from https://octopus.com/downloads and previous versions can be downloaded from https://octopus.com/downloads/previous
What You Need to Do
Octopus Deploy recommends that you upgrade to the latest version (2020.6.4671). You can download the latest version of
If you can't upgrade to the latest version (2020.6.4671):
| If you have feature version... | ...then upgrade to this version |
|---|---|
| 2018.x.x, 2019.x.x, 2020.1.x, 2020.2.x, 2020.3.x | 2020.4.229 or greater |
| 2020.4.x | 2020.4.229 or greater |
| 2020.5.x | 2020.5.256 or greater |
For Octopus Server versions: 0.xx, 1.x.x, 2.x.x, 3.x.x, 4.x.x please contact our support team https://octopus.com/support for advice on upgrading to a supported version.
Mitigation
If you are unable to patch your Octopus Server installation you can effectively mitigate this vulnerability by removing any “CreateFiles” or “AppendData” permissions for “BUILTIN\Users” on the Octopus Server installation directory.
The following links are for the PowerShell commands that can be used to check folder ACLs and update them:
- https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.security/get-acl?view=powershell-7.1
- https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.security/set-acl?view=powershell-7.1
Support
If you have any questions or concerns regarding this advisory, please contact our support team https://octopus.com/support.
Exploitation and Public Announcements
The Octopus Deploy security team is not aware of any malicious use of the vulnerability that is described in this advisory.
A public announcement has been made by DeepSurface Security at https://deepsurface.com/deepsurface-security-advisory-local-privilege-escalation-in-octopus-deploy-on-windows-cve-2021-26556/
Source
This vulnerability was found by Robert Chen from DeepSurface Security.