CyberSecBulletin
CVE-2018-0296Exploited in the wildNVD status: Analyzed

Cisco Adaptive Security Appliance (ASA) Denial-of-Service

Published Updated By the CyberSecBulletin desk

CVE-2018-0296 is a high-severity improper limitation of a pathname to a restricted directory vulnerability in Cisco Adaptive Security Appliance unknown, with a CVSS 3.1 base score of 7.5 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 unknown versions: Cisco Adaptive Security Appliance unknown. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on November 3, 2021, which means attacks have been observed in the wild.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update Adaptive Security Appliance Software to 9.1.7.29 or 9.2.4.33 or 9.4.4.18 or 9.6.4.8, whichever matches your release line, or a later version.
  2. Update Secure Firewall Threat Defense to 6.1.0 or 6.2.2.3, whichever matches your release line, or a later version.
  3. CISA's required action: Apply updates per vendor instructions.
  4. Read the advisory on tools.cisco.com for workarounds and exact fixed builds.
  5. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
Cisco Adaptive Security Appliance unknownCisco Adaptive Security Appliance unknownCisco Adaptive Security Appliance unknownNot stated
CiscoAdaptive Security Appliance Software9.1 up to, but not including, 9.1.7.29; 9.2 up to, but not including, 9.2.4.33; 9.3 up to, but not including, 9.4.4.18; 9.5 up to, but not including, 9.6.4.8; 9.7 up to, but not including, 9.7.1.24; 9.8 up to, but not including, 9.8.2.28; 9.9 up to, but not including, 9.9.2.19.1.7.29, 9.2.4.33, 9.4.4.18, 9.6.4.8, 9.7.1.24, 9.8.2.28
CiscoFirepower Threat Defense6.2.3-85.02; 6.2.3-851Not stated
CiscoSecure Firewall Threat Defense6.0 up to, but not including, 6.1.0; 6.2.1 up to, but not including, 6.2.2.3; 6.2.3; 6.2.3.16.1.0, 6.2.2.3

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
UnchangedImpact stays within the vulnerable component.
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:U/C:N/I:N/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.17.5HighNVD
CVSS 3.17.5HighCISA (ADP)
CVSS 2.05.0MediumNVD

Official description

A vulnerability in the web interface of the Cisco Adaptive Security Appliance (ASA) could allow an unauthenticated, remote attacker to cause an affected device to reload unexpectedly, resulting in a denial of service (DoS) condition. It is also possible on certain software releases that the ASA will not reload, but an attacker could view sensitive system information without authentication by using directory traversal techniques. The vulnerability is due to lack of proper input validation of the HTTP URL. An attacker could exploit this vulnerability by sending a crafted HTTP request to an affected device. An exploit could allow the attacker to cause a DoS condition or unauthenticated disclosure of information. This vulnerability applies to IPv4 and IPv6 HTTP traffic. This vulnerability affects Cisco ASA Software and Cisco Firepower Threat Defense (FTD) Software that is running on the following Cisco products: 3000 Series Industrial Security Appliance (ISA), ASA 1000V Cloud Firewall, ASA 5500 Series Adaptive Security Appliances, ASA 5500-X Series Next-Generation Firewalls, ASA Services Module for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers, Adaptive Security Virtual Appliance (ASAv), Firepower 2100 Series Security Appliance, Firepower 4100 Series Security Appliance, Firepower 9300 ASA Security Module, FTD Virtual (FTDv). Cisco Bug IDs: CSCvi16029.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Limitation of a Pathname to a Restricted Directory

The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

How developers prevent this class of flaw

  • For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
  • Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth.

More Improper Limitation of a Pathname to a Restricted Directory vulnerabilities (CWE-22)

Timeline

  1. CVE record published.
  2. Added to CISA's Known Exploited Vulnerabilities catalogue.
  3. Deadline for US federal agencies to remediate, set by CISA.
  4. CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: partial).
  5. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Technical write-ups (may include proof of concept)

Recent Improper Limitation of a Pathname to a Restricted Directory vulnerabilities

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