How severe is CVE-2021-26956?

CVE-2021-26956 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-26956 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (75th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-26956?

CVE-2021-26956 affects Xcb Project Xcb. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-26956?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-26956 published?

CVE-2021-26956 was published on 2021-02-09 and last updated on 2026-06-17.

CVE-2021-26956

CVE-2021-26956 is a critical-severity vulnerability in Xcb Project Xcb with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (75th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Xcb Project Xcb
Published: 2021-02-09
Last modified: 2026-06-17

Description

An issue was discovered in the xcb crate through 2021-02-04 for Rust. It has a soundness violation because bytes from an X server can be interpreted as any data type returned by xcb::xproto::GetPropertyReply::value.

Frequently asked questions

What is CVE-2021-26956?: An issue was discovered in the xcb crate through 2021-02-04 for Rust. It has a soundness violation because bytes from an X server can be interpreted as any data type returned by xcb::xproto::GetPropertyReply::value.
How severe is CVE-2021-26956?: CVE-2021-26956 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-26956 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (75th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-26956?: CVE-2021-26956 affects Xcb Project Xcb. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-26956?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-26956 published?: CVE-2021-26956 was published on 2021-02-09 and last updated on 2026-06-17.

References

https://rustsec.org/advisories/RUSTSEC-2021-0019.html

Affected products (1)

cpe:2.3:a:xcb_project:xcb:*:*:*:*:*:rust:*:*

More vulnerabilities in Xcb Project Xcb

CVE-2021-26957 — Critical (CVSS 9.8): An issue was discovered in the xcb crate through 2021-02-04 for Rust. It has a soundness violation because there is an…
CVE-2021-26955 — Critical (CVSS 9.8): An issue was discovered in the xcb crate through 2021-02-04 for Rust. It has a soundness violation because…
CVE-2021-26958 — High (CVSS 8.8): An issue was discovered in the xcb crate through 2021-02-04 for Rust. It has a soundness violation because…
CVE-2020-36205 — Medium (CVSS 5.5): An issue was discovered in the xcb crate through 2020-12-10 for Rust. base::Error does not have soundness. Because of…

All CVEs affecting Xcb Project Xcb →