dbcve.org
Gs1900 8 FirmwareOperating system · Zyxel

CVE-2021-35032

HIGH · 7.8 CVSS v3.1 Published 2021-12-28
Fix available
A fix is available. Upgrade to 2.70 or later.
See remediation →
80/100
Remediation priority · High
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A vulnerability in the 'libsal.so' of the Zyxel GS1900 series firmware version 2.60 could allow an authenticated local user to execute arbitrary OS commands via a crafted function call.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-78

User input reaches a shell or system command without being fully separated from the command itself, so an attacker can append their own instructions. Because these run with the application's privileges, it often means full control of the host. The lasting fix is to avoid the shell entirely — call APIs directly and pass arguments as data, never as concatenated strings.

General guidance for the os command injection class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Gs1900 8 FirmwareOperating system
Affected:< 2.70\(aahh.0\)-20211208
Gs1900 8hp FirmwareOperating system
Affected:< 2.70\(aahi.0\)-20211208
Gs1900 10hp FirmwareOperating system
Affected:< 2.70\(aazi.0\)-20211208
Gs1900 16 FirmwareOperating system
Affected:< 2.70\(aahj.0\)-20211208
Gs1900 24e FirmwareOperating system
Affected:< 2.70\(aahk.0\)-20211208
Gs1900 24ep FirmwareOperating system
Affected:< 2.70\(abto.0\)-20211208
Gs1900 24 FirmwareOperating system
Affected:< 2.70\(aahl.0\)-20211208
Gs1900 24hp FirmwareOperating system
Affected:< 2.70\(aahm.0\)-20211208

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2.70 or later
Fixed in 2.70
Vendor patch www.zyxel.com →
Recommended fix High confidence

Firmware version 2.70 (with build numbers dated 20211208: aahh.0, aahi.0, aazi.0, aahj.0, aahk.0, abto.0, aahl.0, aahm.0 depending on model)

  1. Check the current firmware version on the affected GS1900 switch via the web management interface or CLI
  2. Access the Zyxel support portal at https://www.zyxel.com/support/Zyxel_security_advisory_for_OS_command_injection_vulnerabilities_of_switches.shtml to download the fixed firmware version 2.70 with the appropriate build number for your specific model
  3. Log in to the switch web management interface and navigate to the Administration > Firmware Upgrade section
  4. Upload the downloaded firmware file (.bin) to the switch
  5. Initiate the firmware upgrade and wait for the process to complete - do not power off the device during this process
  6. After the switch reboots, verify the new firmware version is installed by checking the system information
Caveat Standard firmware upgrade - ensure to backup configuration before upgrading; brief service interruption during the upgrade process

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $3,200. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-35032 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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