CVE-2020-13753

What it actually does

The bubblewrap sandbox failed to block CLONE_NEWUSER namespace creation and the TIOCSTI ioctl, allowing confusion of xdg-desktop-portal or direct injection into the controlling terminal's input buffer to escape the sandbox.

Why it matters to the business

Attackers can break out of the application sandbox on affected systems, leading to unauthorized access to user data, execution of commands with broader privileges, and increased compromise risk for desktop applications relying on WebKitGTK or WPE WebKit; the issue has been public for over six years with stable but low exploit probability.

How an attack unfolds

An attacker supplies crafted web content or input that triggers the unblocked CLONE_NEWUSER call to confuse xdg-desktop-portal or uses TIOCSTI to inject commands into the terminal buffer, achieving sandbox escape similar to prior terminal injection issues; listed threat actors such as Candiru have been associated with related WebKit exploitation techniques.

How to fix it

Upgrade affected glib packages to the commit 156d249b7b7b4a91068c808c1e7bdc8db5ad3a9b or later; ensure WebKitGTK and WPE WebKit are at version 2.28.3 or newer; apply vendor updates promptly and verify sandbox configurations block the affected syscalls and ioctls.

How to confirm the fix worked

Confirm package versions match or exceed the fixed glib commit; test sandbox isolation by attempting CLONE_NEWUSER and TIOCSTI operations from within the sandbox and verifying they are denied; review build logs and dependency graphs for the corrected glib.

Typical attack path

1. Deliver malicious content to a vulnerable WebKitGTK or WPE WebKit instance
2. Trigger CLONE_NEWUSER namespace creation or TIOCSTI ioctl via sandboxed process
3. Confuse xdg-desktop-portal or inject into terminal input buffer
4. Escape sandbox restrictions to access host resources
5. Execute arbitrary commands or access sensitive data outside the sandbox

How to detect it

Examine system and application logs for unexpected process namespace creations, terminal input injections, or interactions with xdg-desktop-portal originating from WebKit processes; correlate with process creation events showing activity outside expected sandbox boundaries.

What your security team should do

• Apply the glib commit fix or equivalent WebKit updates across all affected systems
• Audit sandbox configurations for WebKit-based applications to enforce namespace and ioctl restrictions
• Monitor upstream WebKitGTK and WPE releases for any follow-on hardening
• Review endpoint logs for signs of prior sandbox escape attempts given the long disclosure window