Security Advisory 2026-22
| Summary | Custom OIDC claims allow subject spoofing and cross-project impersonation |
| Advisory Number | 2026-22 |
| Discovery Date | 06 OCT 2026 |
| Patch Release Date | 08 OCT 2026 |
| Advisory Release Date | 12 NOV 2026 |
| Product | Octopus Server |
| Operating System | Linux and Microsoft Windows |
| Severity | High |
| CVE ID | CVE-2026-116835 |
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 who have upgraded Octopus Server to version 2026.3.15894 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
In affected versions of Octopus Server, insufficient validation of custom claims on OIDC accounts allowed a user with permission to edit accounts to cause Octopus Server to issue signed OIDC tokens that impersonate a different project. This could grant access to external systems, such as cloud providers or other Octopus instances, that trust that project's identity.
The versions of Octopus Server affected by this vulnerability are:
- All 2025.3.x versions AFTER 2025.3.11571
- All 2025.4.x, 2026.1.x versions
- All 2026.2.x versions before 2026.2.13503
- All 2026.3.x versions before 2026.3.15894
Octopus Cloud customers do not need to take any further action as all instances have been updated to the patched version.
Fix
To address this vulnerability, we have released Octopus Server version:
- 2026.2.13503
- 2026.3.15894
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 (2026.3.16117). You can download the latest version of Octopus Server from https://octopus.com/downloads
If you can't upgrade to the latest version (2026.3.16117):
| If you have feature version... | ...then upgrade to this version |
|---|---|
| 2025.3.x, 2025.4.x, 2026.1.x | 2026.2.13503 or greater |
| 2026.2.x | 2026.2.13503 or greater |
| 2026.3.x | 2026.3.15894 or greater |
Mitigation
There is no known mitigation for CVE-2026-116835, it is important to upgrade to a fixed version as soon as possible.
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 public announcements or malicious use of the vulnerability that is described in this advisory.
Source
This vulnerability was found during internal testing by Terry Rossow at Octopus Deploy