# CVE-2026-82731: Unescaped path parameters in AshTypescript generated TypeScript client allow request redirection

> Attackers can redirect generated client requests to malicious hosts, potentially stealing credentials, by exploiting unescaped path parameters in AshTypescript.

- **Severity:** Low 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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 1 Sep 2026
- **Updated:** 1 Sep 2026
- **Also known as:** EEF-CVE-2026-82731, GHSA-6g23-p936-fm2f

## What is CVE-2026-82731?

CVE-2026-82731 is a low-severity vulnerability in ash-project ash_typescript, published on 1 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-601 (URL Redirection to Untrusted Site)

## Which versions are affected by CVE-2026-82731?

1 open source package ship an affected version, including ash_typescript.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `ash_typescript` | Hex | From 0.15.0 | 0.18.0 |

## How do I fix CVE-2026-82731?

Upgrade ash_typescript to 0.18.0 or later.

## Is CVE-2026-82731 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-82731 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-82731 and fix it if it is affected.

What it is: CVE-2026-82731 is a low-severity vulnerability in ash-project ash_typescript, published on 1 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-82731 exists.

Affected packages and fixed versions:
- ash_typescript (Hex): affected from 0.15.0; fixed in 0.18.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-82731/ (Markdown: https://insights.sbomify.com/CVE-2026-82731/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-82731
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-82731
- OSV: https://osv.dev/vulnerability/CVE-2026-82731

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-82731/
Summaries are generated and may contain mistakes; the official description above is the record.