VMG3312-T20A firmware: Improper Neutralization of Special Elements used in an OS Command
CVE-2022-26413 is a high-severity improper neutralization of special elements used in an OS command vulnerability in VMG3312-T20A firmware from Zyxel, with a CVSS 3.1 base score of 8.0 out of 10. It can be exploited from the same local network by an attacker with a low-privileged account, without any action from a user. Affected VMG3312-T20A firmware versions: V5.30(ABFX.5)C0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.7% chance of exploitation within 30 days, higher than 54% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Emg3525-t50b Firmware to 5.50\(abpm.6\)c0 or a later version.
- Update Emg5523-t50b Firmware to 5.50\(abpm.6\)c0 or a later version.
- Update Emg5723-t50k Firmware to 5.50\(abom.7\)c0 or a later version.
- Read the advisory on zyxel.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Zyxel | VMG3312-T20A firmware | V5.30(ABFX.5)C0 | Not stated |
| Zyxel | Emg3525-t50b Firmware | before 5.50\(abpm.6\)c0 | 5.50\(abpm.6\)c0 |
| Zyxel | Emg5523-t50b Firmware | before 5.50\(abpm.6\)c0 | 5.50\(abpm.6\)c0 |
| Zyxel | Emg5723-t50k Firmware | before 5.50\(abom.7\)c0 | 5.50\(abom.7\)c0 |
| Zyxel | Emg6726-b10a Firmware | before 5.13\(abnp.7\)c0 | 5.13\(abnp.7\)c0 |
| Zyxel | Vmg1312-t20b Firmware | before 5.50\(absb.5\)c0 | 5.50\(absb.5\)c0 |
| Zyxel | Vmg3625-t50b Firmware | before 5.50\(abpm.6\)c0 | 5.50\(abpm.6\)c0 |
| Zyxel | Vmg3927-b50a Firmware | before 5.17\(abmt.6\)c0 | 5.17\(abmt.6\)c0 |
| Zyxel | Vmg3927-b50b Firmware | before 5.13\(ably.7\)c0 | 5.13\(ably.7\)c0 |
| Zyxel | Vmg3927-b60a Firmware | before 5.17\(abmt.6\)c0 | 5.17\(abmt.6\)c0 |
| Zyxel | Vmg3927-t50k Firmware | before 5.50\(abom.7\)c0 | 5.50\(abom.7\)c0 |
| Zyxel | Vmg4927-b50a Firmware | before 5.13\(ably.7\)c0 | 5.13\(ably.7\)c0 |
| Zyxel | Vmg8623-t50b Firmware | before 5.50\(abpm.6\)c0 | 5.50\(abpm.6\)c0 |
| Zyxel | Vmg8825-b50a Firmware | before 5.17\(abmt.6\)c0 | 5.17\(abmt.6\)c0 |
| Zyxel | Vmg8825-b50b Firmware | before 5.17\(abny.7\)c0 | 5.17\(abny.7\)c0 |
| Zyxel | Vmg8825-t50k Firmware | before 5.50\(abom.7\)c0 | 5.50\(abom.7\)c0 |
| Zyxel | Vmg8825-b60a Firmware | before 5.17\(abmt.6\)c0 | 5.17\(abmt.6\)c0 |
| Zyxel | Vmg8825-b60b Firmware | before 5.17\(abny.7\)c0 | 5.17\(abny.7\)c0 |
| Zyxel | Xmg3927-b50a Firmware | before 5.17\(abmt.6\)c0 | 5.17\(abmt.6\)c0 |
| Zyxel | Xmg8825-b50a Firmware | before 5.17\(abmt.6\)c0 | 5.17\(abmt.6\)c0 |
| Zyxel | Dx5401-b0 Firmware | before 5.17\(abyo.1\)c0 | 5.17\(abyo.1\)c0 |
| Zyxel | Ex3510-b0 Firmware | before 5.17\(abup.4\)c1 | 5.17\(abup.4\)c1 |
| Zyxel | Ex5401-b0 Firmware | before 5.17\(abyo.1\)c0 | 5.17\(abyo.1\)c0 |
| Zyxel | Ex5501-b0 Firmware | before 5.17\(abry.2\)c0 | 5.17\(abry.2\)c0 |
| Zyxel | Ax7501-b0 Firmware | before 5.17\(abpc.1\)c0 | 5.17\(abpc.1\)c0 |
Version data comes from the organisation that assigned the CVE; 7 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- AdjacentThe attacker must be on the same local network segment.
- 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:A/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.0 | High | CNA (zyxel.com.tw) |
| CVSS 3.1 | 8.0 | High | NVD |
| CVSS 2.0 | 7.7 | High | NVD |
Official description
A command injection vulnerability in the CGI program of Zyxel VMG3312-T20A firmware version 5.30(ABFX.5)C0 could allow a local authenticated attacker to execute arbitrary OS commands on a vulnerable device via a LAN interface.
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
- CVE record published.
- Record last changed materially (score, affected products, status or references).
References
Advisories
Recent Improper Neutralization of Special Elements used in an OS Command vulnerabilities
- 7.8 High severity
- 9.8 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
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