Cisco ASA and FTD Denial of Service
CVE-2024-20353 is a high-severity loop with unreachable exit condition vulnerability in Cisco Adaptive Security Appliance (ASA) Software from Cisco, with a CVSS 3.1 base score of 8.6 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Cisco Adaptive Security Appliance (ASA) Software versions: 9.8.1; 9.8.1.5; 9.8.1.7, and others listed below. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on April 24, 2024, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update asa to 9.14.4.23 or a later version.
- CISA's required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
- Read the advisory on sec.cloudapps.cisco.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Cisco | Cisco Adaptive Security Appliance (ASA) Software | 9.8.1; 9.8.1.5; 9.8.1.7; 9.8.2; 9.8.2.8; 9.8.2.14; 9.8.2.15; 9.8.2.17; and 32 more ranges | Not stated |
| Cisco | Cisco Firepower Threat Defense Software | 6.2.3; 6.2.3.1; 6.2.3.2; 6.2.3.3; 6.2.3.4; 6.2.3.5; 6.2.3.6; 6.2.3.7; and 32 more ranges | Not stated |
| Cisco | asa | 9.8.1 through 9.8.4.48; 9.12.1 through 9.12.4.65; 9.14.1 up to, but not including, 9.14.4.23; 9.15.1 through 9.15.1.21; 9.16.1 through 9.16.4.55; 9.17.1 through 9.17.1.33; 9.18.1 through 9.18.4.8; 9.19.1 through 9.19.1.27; and 1 more ranges | 9.14.4.23 |
| Cisco | firepower_threat_defense_software | 6.2.3 through 6.2.3.18; 6.6.0 through 6.6.7.1; 6.4.0 through 6.4.0.17; 6.7.0 through 6.7.0.3; 7.0.0 through 7.0.6; 7.1.0 through 7.1.0.3; 7.2.0 through 7.2.4.1; 7.3.0 through 7.3.1.1; and 1 more ranges | Not stated |
| Cisco | Adaptive Security Appliance Software | 9.8.1; 9.8.1.5; 9.8.1.7; 9.8.2; 9.8.2.8; 9.8.2.14; 9.8.2.15; 9.8.2.17; and 32 more ranges | Not stated |
| Cisco | Secure Firewall Threat Defense | 6.2.3; 6.2.3.1; 6.2.3.2; 6.2.3.3; 6.2.3.4; 6.2.3.5; 6.2.3.6; 6.2.3.7; and 32 more ranges | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.6 | High | CNA (cisco.com) |
| CVSS 3.1 | 8.6 | High | NVD |
Official description
A vulnerability in the management and VPN web servers for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to incomplete error checking when parsing an HTTP header. An attacker could exploit this vulnerability by sending a crafted HTTP request to a targeted web server on a device. A successful exploit could allow the attacker to cause a DoS condition when the device reloads.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Loop with Unreachable Exit Condition
The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.
More Loop with Unreachable Exit Condition vulnerabilities (CWE-835)
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: partial).
- Deadline for US federal agencies to remediate, set by CISA.
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-20353US Government Resource
Technical write-ups (may include proof of concept)
- blog.talosintelligence.com/arcanedoor-new-espionage-focused-campaign-found-targeting-perimeter-network-device…Exploit, Third Party Advisory
Other vulnerabilities in Cisco Adaptive Security Appliance (ASA) Software
- 9.0 Critical severity
- 8.6 High severity
- 8.6 High severity
- 8.5 High severity
- 7.7 High severity
- 8.6 High severity
Recent Loop with Unreachable Exit Condition vulnerabilities
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
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