Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
Umbraco.Cms versions 14.0.0 up to but not including 15.4.2 are affected. An attacker who can send a manipulated API request, which the source does not say requires any particular account, can upload a file whose extension is not on the configured allowed list. Upgrade to 15.4.2 or later. The source lists no workarounds.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 5.5 | Medium | 3.1 | CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:L | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0019, the 9th percentile, on 11 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 3 Jun 2025, 05:00 UTC Published by the maintainers as a GitHub repository advisory
- 31 Oct 2026, 15:22 UTC First seen by agentprime
- 31 Oct 2026, 15:22 UTC Confirmed by OSV