VDB-185581 · CVE-2021-40118 · GCVE-0-2021-40118

Cisco ASA/Firepower Threat Defense Web Services Interface stack-based overflow

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
7.8	$5k-$25k	0.00

Summaryinfo

A vulnerability marked as critical has been reported in Cisco ASA and Firepower Threat Defense. Affected by this vulnerability is an unknown functionality of the component Web Services Interface. This manipulation causes stack-based overflow. This vulnerability is handled as CVE-2021-40118. The attack can be initiated remotely. There is not any exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Cisco ASA and Firepower Threat Defense (Firewall Software) (the affected version is unknown). Affected by this vulnerability is an unknown code of the component Web Services Interface. The manipulation with an unknown input leads to a stack-based overflow vulnerability. The CWE definition for the vulnerability is CWE-121. A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function). As an impact it is known to affect availability. The summary by CVE is:

A vulnerability in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to trigger a denial of service (DoS) condition. This vulnerability is due to improper input validation when parsing HTTPS requests. An attacker could exploit this vulnerability by sending a malicious HTTPS request to an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.

The weakness was released 10/28/2021 as cisco-sa-asafdt-webvpn-dos-KSqJAKPA. The advisory is shared at tools.cisco.com. This vulnerability is known as CVE-2021-40118 since 08/25/2021. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 08/13/2026).

Upgrading eliminates this vulnerability.

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Productinfo

Type

Firewall Software

Vendor

Cisco

Name

License

commercial

Website

Vendor: https://www.cisco.com/

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.9
VulDB Meta Temp Score: 7.8

VulDB Base Score: 7.5
VulDB Temp Score: 7.2
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 7.5
NVD Vector: 🔍

CNA Base Score: 8.6
CNA Vector (Cisco Systems, Inc.): 🔍

CVSSv2info

AV	AC	Au	C	I	A
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💳	💳	💳	💳	💳	💳
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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: Stack-based overflow
CWE: CWE-121 / CWE-119
CAPEC: 🔍
ATT&CK: 🔍

Physical: No
Local: No
Remote: Yes

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔍

Timelineinfo

08/25/2021 🔍
10/28/2021 +64 days 🔍
10/28/2021 +0 days 🔍
08/13/2026 +1750 days 🔍

Sourcesinfo

Vendor: cisco.com

Advisory: cisco-sa-asafdt-webvpn-dos-KSqJAKPA
Status: Confirmed

CVE: CVE-2021-40118 (🔍)
GCVE (CVE): GCVE-0-2021-40118
GCVE (VulDB): GCVE-100-185581

Entryinfo

Created: 10/28/2021 06:26
Updated: 08/13/2026 08:47
Changes: 10/28/2021 06:26 (49), 11/01/2021 08:35 (19), 07/28/2023 15:09 (2), 08/13/2026 08:47 (18)
Complete: 🔍
Cache ID: 216::103