Zyxel Multiple Firewalls Buffer Overflow
CVE-2023-33010 is a critical-severity buffer copy without checking size of input vulnerability in ATP series firmware from Zyxel, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected ATP series firmware versions: 4.32 through 5.36 Patch 1. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on June 5, 2023, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Atp100 Firmware to 5.36 or a later version.
- Update Atp200 Firmware to 5.36 or a later version.
- Update Atp500 Firmware to 5.36 or a later version.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on zyxel.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Zyxel | ATP series firmware | 4.32 through 5.36 Patch 1 | Not stated |
| Zyxel | USG FLEX series firmware | 4.50 through 5.36 Patch 1 | Not stated |
| Zyxel | USG FLEX 50(W) firmware | 4.25 through 5.36 Patch 1 | Not stated |
| Zyxel | USG20(W)-VPN firmware | 4.25 through 5.36 Patch 1 | Not stated |
| Zyxel | VPN series firmware | 4.30 through 5.36 Patch 1 | Not stated |
| Zyxel | ZyWALL/USG series firmware | 4.25 through 4.73 Patch 1 | Not stated |
| Zyxel | Atp100 Firmware | 4.32 up to, but not including, 5.36; 5.36 | 5.36 |
| Zyxel | Atp200 Firmware | 4.32 up to, but not including, 5.36; 5.36 | 5.36 |
| Zyxel | Atp500 Firmware | 4.32 up to, but not including, 5.36; 5.36 | 5.36 |
| Zyxel | Atp100w Firmware | 4.32 up to, but not including, 5.36; 5.36 | 5.36 |
| Zyxel | Atp700 Firmware | 4.32 up to, but not including, 5.36; 5.36 | 5.36 |
| Zyxel | Atp800 Firmware | 4.32 up to, but not including, 5.36; 5.36 | 5.36 |
| Zyxel | Usg Flex 100 Firmware | 4.50 up to, but not including, 5.36; 5.36 | 5.36 |
| Zyxel | Usg Flex 50 Firmware | 5.36 | Not stated |
| Zyxel | Usg Flex 200 Firmware | 4.50 up to, but not including, 5.36; 5.36 | 5.36 |
| Zyxel | Usg Flex 500 Firmware | 4.50 up to, but not including, 5.36; 5.36 | 5.36 |
| Zyxel | Usg Flex 700 Firmware | 4.50 up to, but not including, 5.36; 5.36 | 5.36 |
| Zyxel | Usg Flex 100w Firmware | 5.36 | Not stated |
| Zyxel | Usg Flex 50w Firmware | 4.25 up to, but not including, 5.36; 5.36 | 5.36 |
| Zyxel | Usg 20w-vpn Firmware | 5.36 | Not stated |
| Zyxel | Vpn100 Firmware | 4.30 up to, but not including, 5.36; 5.36 | 5.36 |
| Zyxel | Vpn50 Firmware | 4.30 up to, but not including, 5.36; 5.36 | 5.36 |
| Zyxel | Vpn300 Firmware | 4.30 up to, but not including, 5.36; 5.36 | 5.36 |
| Zyxel | Vpn1000 Firmware | 4.30 up to, but not including, 5.36; 5.36 | 5.36 |
| Zyxel | Usg20-vpn Firmware | 4.30 up to, but not including, 5.36; 5.36 | 5.36 |
Version data comes from the organisation that assigned the CVE; 4 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
- NoneNo account or login is needed.
- 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:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.8 | Critical | CNA (zyxel.com.tw) |
| CVSS 3.1 | 9.8 | Critical | NVD |
Official description
A buffer overflow vulnerability in the ID processing function in Zyxel ATP series firmware versions 4.32 through 5.36 Patch 1, USG FLEX series firmware versions 4.50 through 5.36 Patch 1, USG FLEX 50(W) firmware versions 4.25 through 5.36 Patch 1, USG20(W)-VPN firmware versions 4.25 through 5.36 Patch 1, VPN series firmware versions 4.30 through 5.36 Patch 1, ZyWALL/USG series firmware versions 4.25 through 4.73 Patch 1, could allow an unauthenticated attacker to cause denial-of-service (DoS) conditions and even a remote code execution on an affected device.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Buffer Copy without Checking Size of Input
The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.
How developers prevent this class of flaw
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
More Buffer Copy without Checking Size of Input vulnerabilities (CWE-120)
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-33010US Government Resource
Other vulnerabilities in ATP series firmware
- 7.2 High severity
- 7.2 High severity
- 8.1 High severity
- 7.2 High severity
- 9.8 Critical severity
Zyxel Multiple Firewalls Path Traversal Exploited
- 7.2 High severity
Recent Buffer Copy without Checking Size of Input vulnerabilities
- 9.8 Critical severity
Zyxel Multiple Firewalls Buffer Overflow Exploited
- 8.1 High severity
- 9.8 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
Spotted an error? Tell us.