CyberSecBulletin
CVE-2020-8195Exploited in the wildNVD status: Analyzed

Citrix ADC, Gateway, and SD-WAN WANOP Appliance Information Disclosure

Published Updated By the CyberSecBulletin desk

CVE-2020-8195 is a medium-severity improper limitation of a pathname to a restricted directory vulnerability in Citrix ADC, Citrix Gateway, Citrix SDWAN WAN-OP, with a CVSS 3.1 base score of 6.5 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. 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 Application Delivery Controller Firmware to 10.5-70.18 or 11.1-64.14 or 12.0-63.21 or 12.1-57.18, whichever matches your release line, or a later version.
  2. Update Netscaler Gateway Firmware to 10.5-70.18 or 11.1-64.14 or 12.0-63.21 or 12.1-57.18, whichever matches your release line, or a later version.
  3. Update Gateway Firmware to 13.0-58.30 or a later version.
  4. CISA's required action: Apply updates per vendor instructions.
  5. Read the advisory on support.citrix.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
Citrix ADC, Citrix Gateway, Citrix SDWAN WAN-OPCitrix ADC, Citrix Gateway, Citrix SDWAN WAN-OPNot specified in the recordNot stated
CitrixApplication Delivery Controller Firmware10.5 up to, but not including, 10.5-70.18; 11.1 up to, but not including, 11.1-64.14; 12.0 up to, but not including, 12.0-63.21; 12.1 up to, but not including, 12.1-57.18; 13.0 up to, but not including, 13.0-58.3010.5-70.18, 11.1-64.14, 12.0-63.21, 12.1-57.18, 13.0-58.30
CitrixNetscaler Gateway Firmware10.5 up to, but not including, 10.5-70.18; 11.1 up to, but not including, 11.1-64.14; 12.0 up to, but not including, 12.0-63.21; 12.1 up to, but not including, 12.1-57.1810.5-70.18, 11.1-64.14, 12.0-63.21, 12.1-57.18
CitrixGateway Firmware13.0 up to, but not including, 13.0-58.3013.0-58.30
CitrixSd-wan Wanop10.2 up to, but not including, 10.2.7; 11.0 up to, but not including, 11.0.3d; 11.1 up to, but not including, 11.1.1a10.2.7, 11.0.3d, 11.1.1a
CitrixGateway Plug-in For Linuxbefore 1.0.0.1371.0.0.137

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
LowA basic user account is enough.
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:L/UI:N/S:U/C:H/I:N/A:N. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.16.5MediumNVD
CVSS 3.16.5MediumCISA (ADP)
CVSS 2.04.0MediumNVD

Official description

Improper input validation in Citrix ADC and Citrix Gateway versions before 13.0-58.30, 12.1-57.18, 12.0-63.21, 11.1-64.14 and 10.5-70.18 and Citrix SDWAN WAN-OP versions before 11.1.1a, 11.0.3d and 10.2.7 resulting in limited information disclosure to low privileged users.

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: no, 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)

Other vulnerabilities in Citrix ADC, Citrix Gateway, Citrix SDWAN WAN-OP

All Citrix ADC, Citrix Gateway, Citrix SDWAN WAN-OP vulnerabilities

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