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CVE-2021-26956

29
FAUCET Score

CVE-2021-26956 describes a critical soundness violation in the Rust xcb crate (through 2021-02-04), where bytes received from an X server can be improperly interpreted as arbitrary data types. This vulnerability carries a CVSS score of 9.8 (CRITICAL), indicating a severe impact with high confidentiality, integrity, and availability compromise, and can be exploited remotely without user interaction. Despite its high severity, there is currently no evidence of active exploitation, publicly available exploit code, or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
<= 2021-02-04CPE matchmatch criteria
cpe:2.3:a:xcb_project:xcb:*:*:*:*:*:rust:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.73%
Probability of exploitation in next 30 days
EPSS Percentile
75.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0173 is in the 63rd percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

rustpatch availablevia ghsa
Product: xcbFixed in: 1.0.0

Vendor Advisories (1)

rustGHSA-mp6r-fgw2-rxfxcritical

Arbitrary return types in xcb

Aug 25, 2021

References

rustsec.org / advisories/RUSTSEC-2021-0019.html
ExploitVendor Advisory