Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:N) | Network: reachable remotely |
| Attack complexity (AC:L) | Low complexity |
| Privileges required (PR:L) | Low privileges required |
| User interaction (UI:N) | No user interaction |
| Scope (S:U) | Scope unchanged |
| Confidentiality (C:H) | High confidentiality impact |
| Integrity (I:H) | High integrity impact |
| Availability (A:H) | High availability impact |
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
About Zyxel Ex5601-T1 Firmware
CVE-2025-13943 affects Zyxel Ex5601-T1 Firmware, a product from Zyxel. Before acting, confirm where Zyxel Ex5601-T1 Firmware runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: A post-authentication command injection vulnerability in the log file download function of the Zyxel EX3301-T0 firmware versions through 5.50(ABVY.7)C0 could allow an authenticated attacker to execute operating system (OS) commands on an affected device.
The weakness class is OS Command Injection. Untrusted input is passed to the operating system shell, letting an attacker run commands.
Based on its CVSS vector, the flaw can be reached over the network, needs some level of access, and needs no user interaction. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | Zyxel Ex5601-T1 Firmware |
| Affected versions | Ex5601-T1 Firmware before 5.70\(acdz.5.1\)c0; Ex7501-B0 Firmware before 5.18\(achn.3.1\)c0; Ex7710-B0 Firmware before 5.18\(acak.1.6\)c0; Gm4100-B0 Firmware before 5.18\(accl.2\)c0; Pm7500-00 Firmware before 5.61\(ackk.1.2\)c0; Vmg3625-T50b Firmware before 5.50\(abpm.9.7\)c0; Vmg4005-B50a Firmware before 5.17\(abqa.3.2\)c0; Vmg4005-B60a Firmware before 5.17\(abqa.3.2\)c0; Ax7501-B1 Firmware before 5.17\(abpc.7.1\)c0; Pe3301-00 Firmware before 5.63\(acmt.2.1\)c0; Pe5301-01 Firmware before 5.63\(acoj.2.1\)c0; Pm3100-T0 Firmware before 5.42\(acbf.4.1\)c0 |
| Published | Feb 24, 2026 |
| Last modified | Jun 17, 2026 |
| Added to CISA KEV | Not listed |
| Assigning CNA | security@zyxel.com.tw |
How to detect it
- Inventory every instance of Zyxel Ex5601-T1 Firmware and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of Zyxel Ex5601-T1 Firmware named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on Zyxel Ex5601-T1 Firmware to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Rank using EPSS and CVSS together with asset exposure and business impact. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
- CWE-78: OS Command Injection More CVEs with this weakness
Technical References
Frequently asked questions
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