CVE-2021-26955: Xcb Unchecked Return Value Vulnerability

CRITICAL
Advisory Identifier: GHSA-3288-cwgw-ch86
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CVSS 9.8
CWE-252
Published
Advisory Summary

CVE-2021-26955 is a CRITICAL (CVSS 9.8) unchecked return value vulnerability (CWE-252: Unchecked Return Value) affecting Xcb libraries in the crates.io ecosystem. The issue involves unchecked return value in xcb. Remediation is available by upgrading affected packages to version 1.0.0.

CVE-2021-26955 at a Glance

CVE Identifier CVE-2021-26955
GHSA Identifier GHSA-3288-cwgw-ch86
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-252: Unchecked Return Value
Affected Product Xcb
Package Ecosystem crates.io
Published Date
Last Updated

Security Impact

CVSS: 9.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2021-26955

To remediate this vulnerability, upgrade all affected Xcb dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

xcb fixed: 1.0.0 
Upgrade xcb to 1.0.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for xcb

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-26955, inspect your project dependencies for Xcb:

inspect dependencies for xcb

Analyze the terminal output to locate any version of Xcb in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.0.0), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-252: Unchecked Return Value, where the product does not check the return value from a method or function, which can prevent it from detecting unexpected states and conditions. In Xcb, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

An issue was discovered in the xcb crate through 2021-02-04 for Rust. It has a soundness violation because xcb::xproto::GetAtomNameReply::name() calls std::str::from_utf8_unchecked() on unvalidated bytes from an X server.

CVE-2021-26955 Affected Xcb Versions

1 component(s)
Fixed Versions:
1.0.0
Product / Package Ecosystem Affected Versions Fixed Version
xcb
 crates.io
< 1.0.0
1.0.0

References

NVD — CVE-2021-26955 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-26955
Xcb Source Repository REPOSITORY
https://github.com/RustSec/advisory-db/issues/653
Xcb Source Repository REPOSITORY
https://github.com/rtbo/rust-xcb
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2021-0019.html

Frequently Asked Questions

What is CVE-2021-26955?
CVE-2021-26955 is a security vulnerability in Xcb involving Unchecked Return Value in xcb under CWE-252: Unchecked Return Value.
Which Xcb versions are affected?
Affected versions include releases prior to 1.0.0 across affected packages: xcb.
What version fixes CVE-2021-26955?
Upgrading to 1.0.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is xcb affected?
Yes, xcb is affected in releases prior to 1.0.0. Upgrade your dependency to 1.0.0 or later.
What is the CVSS score of CVE-2021-26955?
CVE-2021-26955 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2021-26955?
CVE-2021-26955 is classified under CWE-252: Unchecked Return Value (The product does not check the return value from a method or function, which can prevent it from detecting unexpected states and conditions.).
How can I check crates.io dependencies for CVE-2021-26955?
Run the dependency tree command: 'inspect dependencies for xcb'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-3288-cwgw-ch86",
  "modified" : "2021-08-19T17:44:05Z",
  "published" : "2021-08-25T20:53:22Z",
  "aliases" : [ "CVE-2021-26955" ],
  "summary" : "Unchecked Return Value in xcb",
  "details" : "An issue was discovered in the xcb crate through 2021-02-04 for Rust. It has a soundness violation because xcb::xproto::GetAtomNameReply::name() calls std::str::from_utf8_unchecked() on unvalidated bytes from an X server.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "xcb"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.0.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-26955"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/RustSec/advisory-db/issues/653"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/rtbo/rust-xcb"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2021-0019.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-252" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-08-19T17:44:05Z",
    "nvd_published_at" : null
  }
}