Description
Kan 0.5.5 through 0.6.0 contains an unauthenticated server-side request forgery vulnerability in the /api/download/attatchment route due to an incomplete fix for CVE-2026-32255. When S3_ENDPOINT is unset, attackers can pass arbitrary url query parameters to fetch() to read internal services, localhost ports, and cloud instance metadata.
References8
- github.com/kanbn/kan
- github.com/kanbn/kan/blob/v0.6.0/.env.example#L25-L27
- github.com/kanbn/kan/blob/v0.6.0/apps/web/src/pages/api/downloa…
- github.com/kanbn/kan/commit/53397d8e81dc1494d94132848c1f0416f11…
- github.com/kanbn/kan/pull/590
- github.com/kanbn/kan/security/advisories/GHSA-qrx8-9hc6-jvqg
- hackmd.io/@leediay/HyIxU63ofg
- www.vulncheck.com/advisories/kan-0.5.5-through-0.6.0-unauthenti…
Metrics
- CVSS 3.1
-
8.6
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N - CVSS 4.0
-
9.2
CRITICAL
Score source: CNA
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 0% percentile: 37 · as of 11 November 2026
- CWE
- CWE-918
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.