CVE-2021-26955

Name: CVE-2021-26955
Creator: NVD / NIST
Published: 2021-02-09T23:15:13.913+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 1.73%

Last modified Jun 17, 2026

CVE-2021-26955 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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.. EPSS estimates a 1.73% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

1.73%

74.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-252

Affected Software

Vendor	Product	Versions
Xcb Project	Xcb	<= 2021-02-04

References

https://rustsec.org/advisories/RUSTSEC-2021-0019.htmlExploit, Vendor Advisory
https://rustsec.org/advisories/RUSTSEC-2021-0019.htmlExploit, Vendor Advisory

Timeline

Published: Feb 9, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-26955?

How severe is CVE-2021-26955?

CVE-2021-26955 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 1.73% probability of exploitation in the next 30 days.

How do I fix CVE-2021-26955?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-26955?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST