CVE-2021-26958: An issue was discovered in the xcb crate through 2021-02-04 for Rust

Q: How do I fix CVE-2021-26958?

xcb: upgrade to newer than 2021-02-04. Exact commands for each OS are on this page.

Q: Is CVE-2021-26958 being exploited?

CVE-2021-26958 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-26958 affect?

CVE-2021-26958 affects xcb. Severity is high (CVSS 8.8). An issue was discovered in the xcb crate through 2021-02-04 for Rust. It has a soundness violation because transmutation to the wrong type can happen after xcb::base::cast_event uses std::mem::transmute to return a reference to an arbitrary

Q: How urgent is CVE-2021-26958?

Priority 55/100. High severity; Public exploit reference

This month

HIGH 8.8UPGRADE

CVE-2021-26958 is a high-severity flaw (CVSS 8.8) affecting xcb. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in the xcb crate through 2021-02-04 for Rust. It has a soundness violation because transmutation to the wrong type can happen after xcb::base::cast_event uses std::mem::transmute to return a reference to an arbitrary type.

Why this priority

High severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	1.6% (top 24%)
CISA exploited list	No
Weakness	CWE-252
Published	2021-02-09
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: xcb project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-02-09 23:15 UTCPublished CVE record published
2026-06-17 03:44 UTCUpdated Record last modified

xcb project xcb UPGRADE

Affected: <= 2021-02-04

Fixed in: newer than 2021-02-04

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy xcb || rpm -q xcb || xcb --version

2. UPGRADE to newer than 2021-02-04 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade xcb

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade xcb

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-26958?

xcb: upgrade to newer than 2021-02-04. Exact commands for each OS are on this page.

Is CVE-2021-26958 being exploited?

CVE-2021-26958 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-26958 affect?

CVE-2021-26958 affects xcb. Severity is high (CVSS 8.8). An issue was discovered in the xcb crate through 2021-02-04 for Rust. It has a soundness violation because transmutation to the wrong type can happen after xcb::base::cast_event uses std::mem::transmute to return a reference to an arbitrary

How urgent is CVE-2021-26958?

Priority 55/100. High severity; Public exploit reference

Related CVEs

CVE-2021-26957 CRITICAL 9.8 UPGRADE An issue was discovered in the xcb crate through 2021-02-04 for Rust
CVE-2021-26956 CRITICAL 9.8 UPGRADE An issue was discovered in the xcb crate through 2021-02-04 for Rust
CVE-2021-26955 CRITICAL 9.8 UPGRADE An issue was discovered in the xcb crate through 2021-02-04 for Rust
CVE-2020-36205 MEDIUM 5.5 UPGRADE An issue was discovered in the xcb crate through 2020-12-10 for Rust

References

← Back to latest CVEs