# CVE-2026-82731

## Summary

- **CVE ID:** CVE-2026-82731
- **Severity:** LOW
- **CVSS Score:** 2.3 (CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:N/SA:N)
- **CWE:** CWE-601
- **Published:** Sep 1, 2026
- **Last Modified:** Sep 1, 2026

## Description

URL Redirection to Untrusted Site ('Open Redirect') vulnerability in ash-project ash_typescript allows an attacker who controls a path-parameter value to redirect a generated client's request, and the credentials attached to it, to an unintended route or an external origin.

The URL builders in lib/ash_typescript/typed_controller/codegen/route_renderer.ex replace each :param placeholder with a bare template interpolation and never call encodeURIComponent, so the value reaches executeTypedControllerRequest raw. A value containing ../ is normalised away by the fetch URL resolver and reaches a different route, while ? or # truncates the path and can smuggle or override query parameters. For a route whose path begins with a parameter, a value such as /evil.example.com/x yields the protocol-relative URL //evil.example.com/x, sending the request and the credentials from TypedControllerConfig to an attacker-controlled host. Nothing constrains the value at runtime: get_path_param_type/2 emits only a TypeScript type, which is erased.

The query-string path is unaffected, since URLSearchParams.set encodes its own values.

This issue affects ash_typescript: from 0.15.0 before 0.18.0.

## Affected Products

- ash-project — ash_typescript (0.15.0)
- ash-project — ash_typescript (6669e22ece34b4534e706a46d1842f01b68ee23a)

## References

- [CNA](https://github.com/ash-project/ash_typescript/security/advisories/GHSA-6g23-p936-fm2f)
- [CNA](https://cna.erlef.org/cves/CVE-2026-82731.html)
- [CNA](https://osv.dev/vulnerability/EEF-CVE-2026-82731)
- [CNA](https://github.com/ash-project/ash_typescript/commit/5165f752f5f92b755d946f2d1ce750ff69083ffc)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.29%
- **EPSS Percentile:** 21.0

---
_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-09._