CyberSecBulletin
CVE-2022-26531NVD status: Modified

Multiple improper input validation flaws were identified in some CLI commands of Zyxel…

Published Updated By the CyberSecBulletin desk

CVE-2022-26531 is a high-severity improper input validation 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 6.37% chance of exploitation within 30 days, which is in the top 6.24% 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 3.16.1MediumCNA (zyxel.com.tw)
CVSS 3.17.8HighNVD
CVSS 2.04.6MediumNVD

Official description

Multiple improper input validation flaws were identified in some CLI commands 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 cause a buffer overflow or a system crash via a crafted payload.

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

The underlying weakness: Improper Input Validation

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

How developers prevent this class of flaw

  • Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build recognizers for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of allowing parser code to be scattered throughout the program, where it could be subject to errors or inconsistencies that create weaknesses.
  • Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
  • Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.

More Improper Input Validation vulnerabilities (CWE-20)

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 Input Validation vulnerabilities

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