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Rust XCB Connect Functions Can Close File Descriptors

published 1 year ago

Summary

Rust's XCB library has a bug that can cause file descriptors to be closed unexpectedly, leading to I/O errors. This affects developers using XCB version 1.5 or earlier. To fix, upgrade to XCB version 1.6.0 or later, and use the safe alternatives `connect_with_fd` and `connect_with_fd_and_extensions` instead of the old functions.

What to do

Update rtbo xcb to version 1.6.0.

Affected software

Ecosystem	Vendor	Product	Affected versions
rust	rtbo	xcb	< 1.6.0 Fix: upgrade to 1.6.0

Original advisory text

Rust XCB `xcb::Connection::connect_to_fd*` functions violate I/O safety

The API of `xcb::Connection` has constructors which allow an arbitrary `RawFd` to be used as a socket connection. On either failure of these constructors or on the drop of `Connection`, it closes the associated file descriptor. Thus, a program which uses an `OwnedFd` (such as a `UnixStream`) as the file descriptor can close the file descriptor and continue to attempt using it or close an already-closed file descriptor, violating I/O safety.

Starting in version 1.6.0, `xcb` provides `Connection::connect_with_fd` and `Connection::connect_with_fd_and_extensions` as safe alternatives and deprecates the problematic functions.

References

Fix within

Internet-facing 60 days

Internal At next upgrade

Not known to be exploited
Needs hands-on effort to exploit (estimated)
Gives an attacker partial control (estimated)

Severity

1.7 Low

Type

CWE-666Operation on Resource in Wrong Phase of Lifetime

CWE-672Operation on a Resource after Expiration or Release

Timeline

Published22 Aug 2025

Updated13 Mar 2026

First seen6 Mar 2026

Sources

GHSA-655h-hg88-5qmf · GHSA

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