Auth bypass in Octopus Server
CVE-2026-4881
In affected versions of Octopus Server, permissions were not checked correctly resulting in any authenticated user being able to make server level changes using a certain API endpoint despite receiving an error.
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.004 (28.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 28th percentile — 28.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.002
Affected products
- Octopus Server
- Octopus Deploy Server — versions 2023.0.0, 2025.4.0, 2026.1.0
Weakness classification (CWE)
References
- advisories.octopus.com/post/2026/sa2026-04 (Vendor Advisory)
Frequently asked questions
- What is CVE-2026-4881?
- CVE-2026-4881 is a medium-severity vulnerability in Octopus Server, classified under Missing Authorization. CVSS score: 6.5/10. Published 2026-06-04.
- How severe is CVE-2026-4881?
- Medium severity. CVSS v3 base score is 6.5 out of 10.