CyberSecBulletin
CVE-2022-26532NVD status: Modified

USG/ZyWALL series firmware: Improper Neutralization of Special Elements used in an OS Command

Published Updated By the CyberSecBulletin desk

CVE-2022-26532 is a high-severity improper neutralization of special elements used in an OS command vulnerability in USG/ZyWALL series firmware from Zyxel, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. Affected USG/ZyWALL series firmware versions: 4.09 through 4.71. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 4.79% chance of exploitation within 30 days, which is in the top 7.92% of all scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Nsg300 Firmware to 1.33 or a later version.
  2. Update Nsg100 Firmware to 1.33 or a later version.
  3. Update Nsg50 Firmware to 1.33 or a later version.
  4. Read the advisory on zyxel.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
ZyxelUSG/ZyWALL series firmware4.09 through 4.71Not stated
ZyxelUSG FLEX series firmware4.50 through 5.21Not stated
ZyxelATP series firmware4.32 through 5.21Not stated
ZyxelVPN series firmware4.30 through 5.21Not stated
ZyxelNSG series firmware1.00 through 1.33 Patch 4Not stated
ZyxelNXC2500 firmware<= 6.10(AAIG.3)Not stated
ZyxelNAP203 firmware<= 6.25(ABFA.7)Not stated
ZyxelNWA50AX firmware<= 6.25(ABYW.5)Not stated
ZyxelWAC500 firmware<= 6.30(ABVS.2)Not stated
ZyxelWAX510D firmware<= 6.30(ABTF.2)Not stated
ZyxelVpn100 Firmware4.30 through 5.21Not stated
ZyxelVpn1000 Firmware4.30 through 5.21Not stated
ZyxelVpn300 Firmware4.30 through 5.21Not stated
ZyxelVpn50 Firmware4.30 through 5.21Not stated
ZyxelAtp100 Firmware4.32 through 5.21Not stated
ZyxelAtp100w Firmware4.32 through 5.21Not stated
ZyxelAtp200 Firmware4.32 through 5.21Not stated
ZyxelAtp500 Firmware4.32 through 5.21Not stated
ZyxelAtp700 Firmware4.32 through 5.21Not stated
ZyxelAtp800 Firmware4.32 through 5.21Not stated
ZyxelUsg 110 Firmware4.09 through 4.71Not stated
ZyxelUsg 1100 Firmware4.09 through 4.71Not stated
ZyxelUsg 1900 Firmware4.09 through 4.71Not stated
ZyxelUsg 20w Firmware4.09 through 4.71Not stated
ZyxelUsg 20w-vpn Firmware4.09 through 4.71Not stated

Version data comes from the organisation that assigned the CVE; 35 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
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
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

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

Scoring systemScoreSeverityScored by
CVSS 3.17.8HighCNA (zyxel.com.tw)
CVSS 3.17.8HighNVD
CVSS 2.07.2HighNVD

Official description

A argument injection vulnerability in the 'packet-trace' CLI command of Zyxel USG/ZyWALL series firmware versions 4.09 through 4.71, USG FLEX series firmware versions 4.50 through 5.21, ATP series firmware versions 4.32 through 5.21, VPN series firmware versions 4.30 through 5.21, NSG series firmware versions 1.00 through 1.33 Patch 4, NXC2500 firmware version 6.10(AAIG.3) and earlier versions, NAP203 firmware version 6.25(ABFA.7) and earlier versions, NWA50AX firmware version 6.25(ABYW.5) and earlier versions, WAC500 firmware version 6.30(ABVS.2) and earlier versions, and WAX510D firmware version 6.30(ABTF.2) and earlier versions, that could allow a local authenticated attacker to execute arbitrary OS commands by including crafted arguments to the CLI command.

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

The underlying weakness: Improper Neutralization of Special Elements used in an OS Command

The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command before it is sent to a downstream component.

How developers prevent this class of flaw

  • If at all possible, use library calls rather than external processes to recreate the desired functionality.
  • For any data that will be used to generate a command to be executed, keep as much of that data out of external control as possible. For example, in web applications, this may require storing the data locally in the session's state instead of sending it out to the client in a hidden form field.
  • 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.

More Improper Neutralization of Special Elements used in an OS Command vulnerabilities (CWE-78)

Timeline

  1. CVE record published.
  2. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in USG/ZyWALL series firmware

All USG/ZyWALL series firmware vulnerabilities

Recent Improper Neutralization of Special Elements used in an OS Command vulnerabilities

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