ATP series firmware: Integer Overflow or Wraparound
CVE-2023-4398 is a high-severity integer overflow or wraparound vulnerability in ATP series firmware from Zyxel, with a CVSS 3.1 base score of 7.5 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: versions 4.32 through 5.37. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.88% chance of exploitation within 30 days, higher than 60% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of ATP series firmware you run against the affected versions below, and install the vendor's latest release.
- 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 | versions 4.32 through 5.37 | Not stated |
| Zyxel | USG FLEX series firmware | versions 4.50 through 5.37 | Not stated |
| Zyxel | USG FLEX 50(W) series firmware | versions 4.16 through 5.37 | Not stated |
| Zyxel | USG20(W)-VPN series firmware | versions 4.16 through 5.37 | Not stated |
| Zyxel | VPN series firmware | versions 4.30 through 5.37 | Not stated |
| Zyxel | atp_firmware | 4.32 through 5.37 | Not stated |
| Zyxel | usg_flex_firmware | 4.50 through 5.37 | Not stated |
| Zyxel | usg_flex_50w_firmware | 4.16 through 5.37 | Not stated |
| Zyxel | usg20w-vpn_firmware | 4.16 through 5.37 | Not stated |
| Zyxel | vpn_firmware | 5.30 through 5.37 | Not stated |
| Zyxel | Zld | 4.32 through 5.37; 4.50 through 5.37; 4.16 through 5.37; 4.30 through 5.37 | Not stated |
Version data comes from the organisation that assigned the CVE. 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
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.5 | High | CNA (zyxel.com.tw) |
| CVSS 3.1 | 7.5 | High | NVD |
Official description
An integer overflow vulnerability in the source code of the QuickSec IPSec toolkit used in the VPN feature of the Zyxel ATP series firmware versions 4.32 through 5.37, USG FLEX series firmware versions 4.50 through 5.37, USG FLEX 50(W) series firmware versions 4.16 through 5.37, USG20(W)-VPN series firmware versions 4.16 through 5.37, and VPN series firmware versions 4.30 through 5.37, could allow an unauthenticated attacker to cause denial-of-service (DoS) conditions on an affected device by sending a crafted IKE packet.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Integer Overflow or Wraparound
The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.
How developers prevent this class of flaw
- Ensure that all protocols are strictly defined, such that all out-of-bounds behavior can be identified simply, and require strict conformance to the protocol.
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. If possible, choose a language or compiler that performs automatic bounds checking.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Use libraries or frameworks that make it easier to handle numbers without unexpected consequences. Examples include safe integer handling packages such as SafeInt (C++) or IntegerLib (C or C++).
More Integer Overflow or Wraparound vulnerabilities (CWE-190)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
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 Integer Overflow or Wraparound vulnerabilities
- 8.8 High severity
- 7.8 High severity
- 8.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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