# RUSTSEC-2026-0257: Unix `BROWSER` handling allows browser argument injection

> Attacker-controlled URLs can inject browser arguments via BROWSER env var, enabling traffic redirection or remote debugging access.

- **Severity:** Not scored
- **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:** 29 Jul 2026
- **Also known as:** GHSA-2ph8-5cr8-hr33

## What is RUSTSEC-2026-0257?

RUSTSEC-2026-0257 is a command injection vulnerability in webbrowser, published on 29 Jul 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

On Unix platforms handled by `src/unix.rs`, affected versions substitute the
caller-supplied URL into the `BROWSER` environment-variable template before
tokenizing the resulting string with `split_ascii_whitespace()`. If an
application passes an attacker-controlled non-HTTP(S) URL whose parsed form
retains spaces and the effective `BROWSER` template contains `%s`, text that
should remain within one URL argument becomes additional browser arguments.

The issue was reproduced with Chromium by injecting
`--remote-debugging-port`, which exposed a local DevTools endpoint, and
`--proxy-server`, which redirected browser traffic through an
attacker-controlled proxy. The available arguments and resulting impact depend
on the browser launched by the affected application.

Version 1.2.2 fixes the issue by tokenizing the `BROWSER` template before
substituting the URL, preserving the URL as part of a single argument. Users
should upgrade to version 1.2.2 or later. Applications that only need HTTP(S)
URLs can also enable the crate's `hardened` feature as defense in depth.

This issue was reported by
[@dywzju09-blip](https://github.com/dywzju09-blip).

## Which versions are affected by RUSTSEC-2026-0257?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `webbrowser` | crates.io | From 0.0.0-0 | 1.2.2 |

## How do I fix RUSTSEC-2026-0257?

Upgrade webbrowser to 1.2.2 or later.

## Is RUSTSEC-2026-0257 being exploited?

There is no known exploitation of RUSTSEC-2026-0257 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for RUSTSEC-2026-0257 and fix it if it is affected.

What it is: RUSTSEC-2026-0257 is a command injection vulnerability in webbrowser, published on 29 Jul 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: There is no known exploitation of RUSTSEC-2026-0257 in the wild and no public exploit code.

Affected packages and fixed versions:
- webbrowser (crates.io): affected from 0.0.0-0; fixed in 1.2.2

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/RUSTSEC-2026-0257/ (Markdown: https://insights.sbomify.com/RUSTSEC-2026-0257/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/RUSTSEC-2026-0257

---
From sbomify Insights: https://insights.sbomify.com/RUSTSEC-2026-0257/
Summaries are generated and may contain mistakes; the official description above is the record.