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Asyncos CVE-2024-20256

MEDIUM
Cross-site Scripting (XSS) (CWE-79)
2024-05-15 psirt@cisco.com
4.8
CVSS 3.1 · Vendor: cisco
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Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization Output encoding, context-aware escaping
MITRE ATT&CK

2 techniques across 2 tactics: Initial Access, Execution

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

Impact

CVSS score of 4.8 (MEDIUM). Attack characteristics: network attack vector, low complexity, high privileges required, user interaction required.

Exploit ScenarioDerived

A remote attacker could inject malicious scripts into web pages viewed by other users by sending crafted requests to the affected application.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.3% exploitation probability (EPSS)

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AnalysisAI

A vulnerability in the web-based management interface of Cisco AsyncOS Software for Cisco Secure Email and Web Manager and Secure Web Appliance could allow an authenticated, remote attacker to. Rated medium severity (CVSS 4.8), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Sanitize all user input, use Content-Security-Policy headers, encode output contextually (HTML, JS, URL). Use frameworks with built-in XSS protection.

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 Cross-Site Scripting (XSS) (CWE-79), which allows attackers to inject malicious scripts into web pages viewed by other users. A vulnerability in the web-based management interface of Cisco AsyncOS Software for Cisco Secure Email and Web Manager and Secure Web Appliance could allow an authenticated, remote attacker to conduct an XSS attack against a user of the interface. This vulnerability is due to insufficient validation of user input. An attacker could exploit this vulnerability by persuading a user of an affected interface to click a crafted link. A successful exploit could allow the attacker to execute arbitrary script code in the context of the affected interface or access sensitive, browser-based information. Affected products include: Cisco Asyncos, Cisco Secure Email And Web Manager Virtual Appliance M100V, Cisco Secure Email And Web Manager Virtual Appliance M300V, Cisco Secure Email And Web Manager Virtual Appliance M600V.

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Severity by source

Vendor (cisco) PRIMARY 4.8 MEDIUM
AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

Primary rating from Vendor (cisco) · only source for this CVE.

CVSS VectorVendor: cisco

Attack Vector
Network
Attack Complexity
Low
Privileges Required
High
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

DescriptionCVE.org

A vulnerability in the web-based management interface of Cisco AsyncOS Software for Cisco Secure Email and Web Manager and Secure Web Appliance could allow an authenticated, remote attacker to conduct an XSS attack against a user of the interface. This vulnerability is due to insufficient validation of user input. An attacker could exploit this vulnerability by persuading a user of an affected interface to click a crafted link. A successful exploit could allow the attacker to execute arbitrary script code in the context of the affected interface or access sensitive, browser-based information.

Threat Intelligence Overview

EPSS Score
0.3%
Top 79% exploitable
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 MEDIUM
CISA KEV No
Public POC No
EPSS 0.3%
Patch available No
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
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
None
System Exposure· derived
Open
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

24
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +24
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Cross-Site Scripting occurs when an application accepts untrusted data and sends it to a web browser without proper validation or encoding.

Affected Products (CPE)CVE.org

cpe:2.3:o:cisco:asyncos:11.7.0-406:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:11.7.0-418:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:11.7.1-006:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:11.7.1-020:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:11.7.1-049:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:11.7.2-011:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:11.8.0-414:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:11.8.1-023:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:11.8.3-018:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:11.8.3-021:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:12.0.1-268:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:12.0.3-007:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:12.5.1-011:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:12.5.2-007:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:12.5.4-005:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:12.5.5-004:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:12.5.6-008:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:14.0.2-012:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:14.0.3-014:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asyncos:14.0.4-005:*:*:*:*:*:*:*
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