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Ios Xe CVE-2025-20363

CRITICAL
Heap-based Buffer Overflow (CWE-122)
2025-09-25 psirt@cisco.com
9.0
CVSS 3.1 · Vendor: cisco
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Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A06:2021 - Vulnerable and Outdated Components
ASVS 5.0
V15 - Secure Coding and Architecture Heap buffer bounds checking
MITRE ATT&CK

1 technique across 1 tactic: 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 9.0 (CRITICAL). Attack characteristics: network attack vector, high complexity, no privileges required, no user interaction not required. EPSS exploitation probability: 5.66%.

Exploit ScenarioDerived

This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the critical-severity affected system.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.
No patch listed yet 5.7% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 28, 2026

A vulnerability in the web services of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, Cisco Secure Firewall Threat Defense (FTD) Software, Cisco IOS Software, Cisco IOS XE. Rated critical severity (CVSS 9.0), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

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 under CWE-122. A vulnerability in the web services of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, Cisco Secure Firewall Threat Defense (FTD) Software, Cisco IOS Software, Cisco IOS XE Software, and Cisco IOS XR Software could allow an unauthenticated, remote attacker (Cisco ASA and FTD Software) or authenticated, remote attacker (Cisco IOS, IOS XE, and IOS XR Software) with low user privileges to execute arbitrary code on an affected device. This vulnerability is due to improper validation of user-supplied input in HTTP requests. An attacker could exploit this vulnerability by sending crafted HTTP requests to a targeted web service on an affected device after obtaining additional information about the system, overcoming exploit mitigations, or both. A successful exploit could allow the attacker to execute arbitrary code as root, which may lead to the complete compromise of the affected device. For more information about this vulnerability, see the Details ["#details"] section of this advisory. Affected products include: Cisco Ios Xr, Cisco Adaptive Security Appliance Software, Cisco Ios, Cisco Ios Xe, Cisco Firepower Threat Defense.

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Severity by source

Vendor (cisco) PRIMARY 9.0 CRITICAL
AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

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

CVSS VectorVendor: cisco

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

DescriptionCVE.org

A vulnerability in the web services of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, Cisco Secure Firewall Threat Defense (FTD) Software, Cisco IOS Software, Cisco IOS XE Software, and Cisco IOS XR Software could allow an unauthenticated, remote attacker (Cisco ASA and FTD Software) or authenticated, remote attacker (Cisco IOS, IOS XE, and IOS XR Software) with low user privileges to execute arbitrary code on an affected device. This vulnerability is due to improper validation of user-supplied input in HTTP requests. An attacker could exploit this vulnerability by sending crafted HTTP requests to a targeted web service on an affected device after obtaining additional information about the system, overcoming exploit mitigations, or both. A successful exploit could allow the attacker to execute arbitrary code as root, which may lead to the complete compromise of the affected device. For more information about this vulnerability, see the Details ["#details"] section of this advisory.

Executive ViewAI

Why It Matters

CVE-2025-20363 presents critical security risk, a heap-based buffer overflow vulnerability rated CVSS 9.0. Exploitation could allow attackers to corrupt memory, crash the application, or potentially execute arbitrary code. Organizations should apply vendor updates immediately when available and implement compensating controls in the interim.

Business Impact: Severe
Compensating Controls

Apply vendor patch. If immediate patching is not feasible: (1) Enable ASLR and DEP where available; (2) Implement network segmentation; (3) Monitor for exploitation indicators.

Threat Intelligence Overview

EPSS Score
5.7%
Top 10% exploitable
Data Quality
3 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 CRITICAL
CISA KEV No
Public POC No
EPSS 5.7%
Patch available No
Active threat No
Deciding rule
CRITICAL severity
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
Very High

Priority Score

51
Low Medium High Critical
KEV: 0
EPSS: +6
CVSS: +45
PoC: 0
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.

A heap overflow occurs when a program writes data beyond the bounds of a buffer allocated in the heap memory region.

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.

Affected Products (CPE)CVE.org

cpe:2.3:o:cisco:ios_xr:6.5.1:*:*:*:*:*:x86:*
cpe:2.3:o:cisco:ios_xr:6.5.2:*:*:*:*:*:x86:*
cpe:2.3:o:cisco:ios_xr:6.5.3:*:*:*:*:*:x86:*
cpe:2.3:o:cisco:ios_xr:6.6.2:*:*:*:*:*:x86:*
cpe:2.3:o:cisco:ios_xr:6.6.3:*:*:*:*:*:x86:*
cpe:2.3:o:cisco:ios_xr:6.6.25:*:*:*:*:*:x86:*
cpe:2.3:o:cisco:ios_xr:6.7.1:*:*:*:*:*:x86:*
cpe:2.3:o:cisco:ios_xr:6.7.2:*:*:*:*:*:x86:*
cpe:2.3:o:cisco:ios_xr:6.7.3:*:*:*:*:*:x86:*
cpe:2.3:o:cisco:ios_xr:6.8.1:*:*:*:*:*:x86:*
cpe:2.3:o:cisco:ios_xr:6.8.2:*:*:*:*:*:x86:*
cpe:2.3:o:cisco:ios_xr:6.9.1:*:*:*:*:*:x86:*
cpe:2.3:o:cisco:ios_xr:6.9.2:*:*:*:*:*:x86:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
+ 8 more

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