Security Advisory 2021-01
|Summary||Local privilege escalation in Octopus Server (CVE-2021-26556)|
|Discovery Date||01 Jan 2021|
|Patch Release Date||07 Mar 2021|
|Advisory Release Date||10 Mar 2021|
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.
Octopus Deploy has given this vulnerability a high rating. This rating was given according to the Octopus Deploy security 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.
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
All 2018.x.x, 2019.x.x, 2020.1.x, 2020.2.x, 2020.3.x versions
All 2020.4.x versions before 2020.4.229
All 2020.5.x versions before 2020.5.256
This issue can be tracked here: https://github.com/OctopusDeploy/Issues/issues/6786
To address this vulnerability, we have released Octopus Server versions:
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.
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:
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/
This vulnerability was found by Robert Chen from DeepSurface Security.