CyberSecBulletin
CVE-2022-43390NVD status: Modified

NR7101 firmware: Improper Neutralization of Special Elements used in an OS Command

Published Updated By the CyberSecBulletin desk

CVE-2022-43390 is a high-severity improper neutralization of special elements used in an OS command vulnerability in NR7101 firmware from Zyxel, with a CVSS 3.1 base score of 8.8 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. Affected NR7101 firmware versions: < V1.15(ACCC.3)C0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 1.12% chance of exploitation within 30 days, higher than 67% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Lte7480-m804 Firmware to 1.00\(abra.6\)c0 or a later version.
  2. Update Lte7490-m904 Firmware to 1.00\(abqy.5\)c0 or a later version.
  3. Update Nebula Nr5101 Firmware to 1.15\(accg.3\)c0 or a later version.
  4. Read the advisory on zyxel.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
ZyxelNR7101 firmware< V1.15(ACCC.3)C0Not stated
ZyxelLte7480-m804 Firmwarebefore 1.00\(abra.6\)c01.00\(abra.6\)c0
ZyxelLte7490-m904 Firmwarebefore 1.00\(abqy.5\)c01.00\(abqy.5\)c0
ZyxelNebula Nr5101 Firmwarebefore 1.15\(accg.3\)c01.15\(accg.3\)c0
ZyxelNebula Nr7101 Firmwarebefore 1.15\(accc.3\)c01.15\(accc.3\)c0
ZyxelNr5101 Firmwarebefore 1.00\(abvc.6\)c01.00\(abvc.6\)c0
ZyxelNr7102 Firmwarebefore 1.00\(abyd.2\)c01.00\(abyd.2\)c0
ZyxelDx3301-t0 FirmwareNot specified in the recordNot stated
ZyxelDx4510-b1 FirmwareNot specified in the recordNot stated
ZyxelDx5401-b0 FirmwareNot specified in the recordNot stated
ZyxelEmg3525-t50b FirmwareNot specified in the recordNot stated
ZyxelEmg5523-t50b FirmwareNot specified in the recordNot stated
ZyxelEmg5723-t50k FirmwareNot specified in the recordNot stated
ZyxelEx3301-t0 FirmwareNot specified in the recordNot stated
ZyxelEx3510-b0 Firmwarebefore 5.17\(abup.7\)c05.17\(abup.7\)c0
ZyxelEx5401-b0 FirmwareNot specified in the recordNot stated
ZyxelEx5501-b0 FirmwareNot specified in the recordNot stated
ZyxelEx5510-b0 Firmwarebefore 5.17\(abqx.7\)c05.17\(abqx.7\)c0
ZyxelEx5512-t0 FirmwareNot specified in the recordNot stated
ZyxelEx5600-t1 FirmwareNot specified in the recordNot stated
ZyxelEx5601-t0 FirmwareNot specified in the recordNot stated
ZyxelEx5601-t1 FirmwareNot specified in the recordNot stated
ZyxelVmg3927-t50k FirmwareNot specified in the recordNot stated
ZyxelVmg4005-b50a FirmwareNot specified in the recordNot stated
ZyxelVmg4005-b60a FirmwareNot specified in the recordNot stated

Version data comes from the organisation that assigned the CVE; 14 further products are omitted here. 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
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

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

Scoring systemScoreSeverityScored by
CVSS 3.15.4MediumCNA (zyxel.com.tw)
CVSS 3.18.8HighNVD

Official description

A command injection vulnerability in the CGI program of Zyxel NR7101 firmware prior to V1.15(ACCC.3)C0, which could allow an authenticated attacker to execute some OS commands on a vulnerable device by sending a crafted HTTP request.

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. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in NR7101 firmware

All NR7101 firmware vulnerabilities

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

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