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Xmill CVE-2021-21815

HIGH
Out-of-bounds Write (CWE-787)
2021-08-13 talos-cna@cisco.com
7.8
CVSS 3.1 · NVD
View

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Bounds checking, write limits
MITRE ATT&CK

2 techniques across 2 tactics: Execution, Privilege Escalation

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Impact

CVSS score of 7.8 (HIGH). Attack characteristics: local attack vector, low complexity, low privileges required, no user interaction not required. Public proof-of-concept exploit code is available.

Exploit ScenarioDerived

A local attacker with access to the system could write data beyond allocated buffer boundaries leading to code execution or crashes.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
No patch listed yet 0.3% exploitation probability (EPSS)

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AnalysisAI

A stack-based buffer overflow vulnerability exists in the command-line-parsing HandleFileArg functionality of AT&T Labs' Xmill 0.7. Rated high severity (CVSS 7.8), this vulnerability is 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 write boundaries, use memory-safe languages, enable compiler protections (ASLR, stack canaries).

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

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 Write (CWE-787), which allows attackers to write data beyond allocated buffer boundaries leading to code execution or crashes. A stack-based buffer overflow vulnerability exists in the command-line-parsing HandleFileArg functionality of AT&T Labs' Xmill 0.7. Within the function HandleFileArg the argument filepattern is under control of the user who passes it in from the command line. filepattern is passed directly to strcpy copying the path provided by the user into a staticly sized buffer without any length checks resulting in a stack-buffer overflow. An attacker can provide malicious input to trigger this vulnerability. Affected products include: Att Xmill.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 7.8 HIGH
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

DescriptionNVD

A stack-based buffer overflow vulnerability exists in the command-line-parsing HandleFileArg functionality of AT&T Labs' Xmill 0.7. Within the function HandleFileArg the argument filepattern is under control of the user who passes it in from the command line. filepattern is passed directly to strcpy copying the path provided by the user into a staticly sized buffer without any length checks resulting in a stack-buffer overflow. An attacker can provide malicious input to trigger this vulnerability.

Threat Intelligence Overview

EPSS Score
0.3%
Top 75% exploitable
Exploit
POC
Public exploit code exists
Data Quality
2 sources
Confidence: Low

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 HIGH
CISA KEV No
Public POC Yes
EPSS 0.3%
Patch available No
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
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
Small
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

59
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +39
PoC: +20
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

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.

Memory corruption occurs when a program writes data beyond the boundaries of allocated memory regions or accesses memory in unintended ways, violating the integrity of the process's address space.

Affected Products (CPE)NVD

cpe:2.3:a:att:xmill:0.7:*:*:*:*:*:*:*

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