PT-2021-17199 · Xcb · Xcb

Published 2021-02-04 · Updated 2021-08-25 · CVE-2021-26958

Positive Technologies (AI Summary)

CVSS v3.1

8.8

High

Base vector

AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Name of the Vulnerable Software and Affected Versions: xcb crate through 2021-02-04 for Rust

Description: The issue concerns a soundness violation in the xcb crate, which can lead to transmutation to the wrong type after using std::mem::transmute to return a reference to an arbitrary type. Specifically, the functions xcb::xproto::GetPropertyReply::value() and xcb::xproto::GetAtomNameReply::name() are affected. The value() function returns a slice of type T where T is an unconstrained type parameter, and the raw bytes received from the X11 server are interpreted as the requested type. The name() function calls std::str::from utf8 unchecked() on unvalidated bytes from an X server. Additionally, there is an out-of-bounds read in xcb::xproto::change property() when the format and type arguments do not match the intended use.

Recommendations: For the xcb crate through 2021-02-04 for Rust:

• As a temporary workaround, consider restricting the use of the xcb::xproto::GetPropertyReply::value() function to only call it with the intended types, which are u8, u16, and u32.
• Avoid using the xcb::xproto::GetAtomNameReply::name() function until the issue is resolved.
• Restrict the use of the xcb::xproto::change property() function to only call it with one of the intended argument combinations, which are format = 8 and T = u8, format = 16 and T = u16, or format = 32 and T = u32.
• Users are advised to only cast to the event structs provided by the xcb crate using the xcb::base::cast event() function. At the moment, there is no information about a newer version that contains a fix for this vulnerability.

Exploit

Out of bounds Read

Unchecked Return Value

Weakness Enumeration

CWE-125

CWE-252

CWE-657

Related Identifiers

CVE-2021-26958

GHSA-2XPG-3HX4-FM9R

GHSA-3288-CWGW-CH86

GHSA-3CJ3-JRRP-9RXF

GHSA-MP6R-FGW2-RXFX

RUSTSEC-2021-0019

Affected Products

Xcb

References · 24

• 🔥 https://rustsec.org/advisories/RUSTSEC-2021-0019.html · Exploit
• https://osv.dev/vulnerability/GHSA-3cj3-jrrp-9rxf · Vendor Advisory
• https://osv.dev/vulnerability/CVE-2021-26958 · Vendor Advisory
• https://osv.dev/vulnerability/RUSTSEC-2021-0019 · Vendor Advisory
• https://osv.dev/vulnerability/GHSA-3288-cwgw-ch86 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2021-26958 · Security Note
• https://nvd.nist.gov/vuln/detail/CVE-2021-26956 · Security Note
• https://osv.dev/vulnerability/GHSA-mp6r-fgw2-rxfx · Vendor Advisory
• https://security-tracker.debian.org/tracker/CVE-2021-26958 · Vendor Advisory
• https://osv.dev/vulnerability/GHSA-2xpg-3hx4-fm9r · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2021-26957 · Security Note
• https://osv.dev/vulnerability/UBUNTU-CVE-2021-26958 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2021-26955 · Security Note
• https://osv.dev/vulnerability/DEBIAN-CVE-2021-26958 · Vendor Advisory
• https://ubuntu.com/security/CVE-2021-26958 · Vendor Advisory