What is the CVSS score of CVE-2021-26957?

CVE-2021-26957 has a CVSS 3.1 base score of 9.8 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 1.8%.

Is there a public PoC exploit available for CVE-2021-26957?

Yes, a public proof-of-concept exploit is available for CVE-2021-26957. Prioritise patching immediately. EPSS: 1.8%.

Is there a patch available for CVE-2021-26957?

Yes, a patch is available for CVE-2021-26957. Update the affected software to the latest version immediately.

Xcb CVE-2021-26957

CRITICAL

Out-of-bounds Read (CWE-125)

2021-02-09 cve@mitre.org

Buffer Overflow Information Disclosure Xcb Xcb Project

9.8

CVSS 3.1 · NVD

View

Vulnerability Assessment

Weakness	CWE CWE-125 ASVS 5.0 V15 - Secure Coding and Architecture Bounds checking, read limits MITRE ATT&CK 1 technique across 1 tactic: Collection The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS score of 9.8 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. Public proof-of-concept exploit code is available.
Exploit ScenarioDerived	A remote attacker could read data from memory outside the intended buffer boundaries by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

Act Now Prioritize within 24-48h. Why: CRITICAL severity + public POC available.

Patch available 1.8% exploitation probability (EPSS)

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AnalysisAI

An issue was discovered in the xcb crate through 2021-02-04 for Rust. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Validate array indices and buffer lengths. Use memory-safe languages. Enable AddressSanitizer during testing.

Affected Packages

cargo xcb fix: 1.0.0

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in cargo

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as Out-of-bounds Read (CWE-125), which allows attackers to read data from memory outside the intended buffer boundaries. An issue was discovered in the xcb crate through 2021-02-04 for Rust. It has a soundness violation because there is an out-of-bounds read in xcb::xproto::change_property(), as demonstrated by a format=32 T=u8 situation where out-of-bounds bytes are sent to an X server. Affected products include: Xcb Project Xcb. Version information: through 2021.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 9.8 CRITICAL

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

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

DescriptionNVD

An issue was discovered in the xcb crate through 2021-02-04 for Rust. It has a soundness violation because there is an out-of-bounds read in xcb::xproto::change_property(), as demonstrated by a format=32 T=u8 situation where out-of-bounds bytes are sent to an X server.

Threat Intelligence Overview

EPSS Score

1.8%

Top 25% exploitable

Exploit

POC

Public exploit code exists

Data Quality

2 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity CRITICAL

CISA KEV No

Public POC Yes

EPSS 1.8%

Patch available Yes

Active threat No

Deciding rule

CRITICAL severity + public POC available

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

Poc

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +2

CVSS: +49

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Buffer Overflow HIGH

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.