CyberSecBulletin
CVE-2020-3452Exploited in the wildNVD status: Analyzed

Cisco ASA and FTD Read-Only Path Traversal

Published Updated By the CyberSecBulletin desk

CVE-2020-3452 is a high-severity improper limitation of a pathname to a restricted directory vulnerability in Cisco Adaptive Security Appliance (ASA) Software from Cisco, 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. The record lists versions 9.6.4.42, 9.8.4.20, 9.9.2.74 as the first without the flaw, so updating Cisco Adaptive Security Appliance (ASA) Software to one of those releases or later removes the exposure. 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 Cisco Adaptive Security Appliance (ASA) Software to 9.6.4.42 or 9.8.4.20 or 9.9.2.74 or 9.10.1.42, whichever matches your release line, or a later version.
  2. Update Adaptive Security Appliance Software to 9.6.4.42 or 9.8.4.20 or 9.9.2.74 or 9.10.1.42, whichever matches your release line, or a later version.
  3. Update Secure Firewall Threat Defense to 6.2.3.16 or 6.3.0.6 or 6.4.0.10 or 6.5.0.5, whichever matches your release line, or a later version.
  4. CISA's required action: Apply updates per vendor instructions.
  5. Read the advisory on tools.cisco.com for workarounds and exact fixed builds.
  6. 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
CiscoCisco Adaptive Security Appliance (ASA) Softwarebefore 9.6.4.42; before 9.8.4.20; before 9.9.2.74; before 9.10.1.42; before 9.13.1.10; before 9.14.1.109.6.4.42, 9.8.4.20, 9.9.2.74, 9.10.1.42, 9.13.1.10, 9.14.1.10
CiscoAdaptive Security Appliance Software9.6 up to, but not including, 9.6.4.42; 9.8 up to, but not including, 9.8.4.20; 9.9 up to, but not including, 9.9.2.74; 9.10 up to, but not including, 9.10.1.42; 9.12 up to, but not including, 9.12.3.12; 9.13 up to, but not including, 9.13.1.10; 9.14 up to, but not including, 9.14.1.109.6.4.42, 9.8.4.20, 9.9.2.74, 9.10.1.42, 9.12.3.12, 9.13.1.10
CiscoSecure Firewall Threat Defense6.2.3 up to, but not including, 6.2.3.16; 6.3.0 up to, but not including, 6.3.0.6; 6.4.0 up to, but not including, 6.4.0.10; 6.5.0 up to, but not including, 6.5.0.5; 6.6.0 up to, but not including, 6.6.0.16.2.3.16, 6.3.0.6, 6.4.0.10, 6.5.0.5, 6.6.0.1

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
HighAll data handled by the component can be read.
Integrity
NoneNothing can be modified.
Availability
NoneAvailability is not affected.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.17.5HighCNA (cisco.com)
CVSS 3.17.5HighNVD
CVSS 2.05.0MediumNVD

Official description

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 conduct directory traversal attacks and read sensitive files on a targeted system. The vulnerability is due to a lack of proper input validation of URLs in HTTP requests processed by an affected device. An attacker could exploit this vulnerability by sending a crafted HTTP request containing directory traversal character sequences to an affected device. A successful exploit could allow the attacker to view arbitrary files within the web services file system on the targeted device. The web services file system is enabled when the affected device is configured with either WebVPN or AnyConnect features. This vulnerability cannot be used to obtain access to ASA or FTD system files or underlying operating system (OS) files.

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

Other vulnerabilities in Cisco Adaptive Security Appliance (ASA) Software

All Cisco Adaptive Security Appliance (ASA) Software vulnerabilities

Recent Improper Limitation of a Pathname to a Restricted Directory vulnerabilities

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