Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
Go standard library (os package) versions before 1.26.9, and 1.27.0 before 1.27.2, are vulnerable on Windows. When the target of Root.Mkdir or Root.MkdirAll is a junction pointing to an empty location, a directory can be created at the junction target even when it lies outside the root. Upgrade to Go 1.26.9 or 1.27.2.
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 |
|---|---|---|---|---|
| 9.8 | Critical | 3.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H | ADP (CISA-ADP) |
- CISA KEV Not listed.
- EPSS 0.0055, the 46th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:12 UTC First seen by agentprime
- 31 Oct 2026, 14:12 UTC Confirmed by OSV