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.
- 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
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.
Which versions are affected by RUSTSEC-2026-0257?
1 open source package ship an affected version, including webbrowser.
| Package | 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.
Upgrade, and pass arguments to programs as a list instead of through a shell. More about Command injection.
Is RUSTSEC-2026-0257 being exploited?
There is no known exploitation of RUSTSEC-2026-0257 in the wild and no public exploit code.
Sources
Also known as GHSA-2ph8-5cr8-hr33.