Improper input validation in Zyxel ATP series firmware
Priority LOW 24CWE-20Published · Updated
Key facts
- Attack vector
- Local
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- High · None · None
- Fix status
- No fix listed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA.
Summary
An improper input validation vulnerability in the “Quagga” package 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 authenticated local attacker to access configuration files on an affected device.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00243 15th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Zyxel | ATP series firmware | versions 4.32 through 5.37 | — | No fix listed | CNA |
| Zyxel | USG FLEX series firmware | versions 4.50 through 5.37 | — | No fix listed | CNA |
| Zyxel | USG FLEX 50(W) series firmware | versions 4.16 through 5.37 | — | No fix listed | CNA |
| Zyxel | USG20(W)-VPN series firmware | versions 4.16 through 5.37 | — | No fix listed | CNA |
| Zyxel | VPN series firmware | versions 4.30 through 5.37 | — | No fix listed | CNA |
- ATP series firmware VendorZyxel Affected versions 4.32 through 5.37 Fixed in — No fix listed CNA
- USG FLEX series firmware VendorZyxel Affected versions 4.50 through 5.37 Fixed in — No fix listed CNA
- USG FLEX 50(W) series firmware VendorZyxel Affected versions 4.16 through 5.37 Fixed in — No fix listed CNA
- USG20(W)-VPN series firmware VendorZyxel Affected versions 4.16 through 5.37 Fixed in — No fix listed CNA
- VPN series firmware VendorZyxel Affected versions 4.30 through 5.37 Fixed in — No fix listed CNA
CPE configurations NVD · 23
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:zyxel:zld:*:*:*:*:*:*:*:* | 4.32 – 5.37 | Vulnerable | Zyxel |
| cpe:2.3:h:zyxel:atp100:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:h:zyxel:atp100w:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:h:zyxel:atp200:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:h:zyxel:atp500:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:h:zyxel:atp700:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:h:zyxel:atp800:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:o:zyxel:zld:*:*:*:*:*:*:*:* | 4.50 – 5.37 | Vulnerable | Zyxel |
| cpe:2.3:h:zyxel:usg_flex_100:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:h:zyxel:usg_flex_100w:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
- cpe:2.3:o:zyxel:zld:*:*:*:*:*:*:*:* Versions 4.32 – 5.37 Vulnerable ·Zyxel
- cpe:2.3:h:zyxel:atp100:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:h:zyxel:atp100w:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:h:zyxel:atp200:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:h:zyxel:atp500:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:h:zyxel:atp700:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:h:zyxel:atp800:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:o:zyxel:zld:*:*:*:*:*:*:*:* Versions 4.50 – 5.37 Vulnerable ·Zyxel
- cpe:2.3:h:zyxel:usg_flex_100:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:h:zyxel:usg_flex_100w:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
Show 13 more CPE
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:h:zyxel:usg_flex_200:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:h:zyxel:usg_flex_50:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:h:zyxel:usg_flex_500:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:h:zyxel:usg_flex_50w:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:h:zyxel:usg_flex_700:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:o:zyxel:zld:*:*:*:*:*:*:*:* | 4.16 – 5.37 | Vulnerable | Zyxel |
| cpe:2.3:h:zyxel:usg_20w-vpn:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:h:zyxel:vpn50w:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:o:zyxel:zld:*:*:*:*:*:*:*:* | 4.30 – 5.37 | Vulnerable | Zyxel |
| cpe:2.3:h:zyxel:vpn100:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:h:zyxel:vpn1000:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:h:zyxel:vpn300:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
| cpe:2.3:h:zyxel:vpn50:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Zyxel |
- cpe:2.3:h:zyxel:usg_flex_200:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:h:zyxel:usg_flex_50:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:h:zyxel:usg_flex_500:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:h:zyxel:usg_flex_50w:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:h:zyxel:usg_flex_700:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:o:zyxel:zld:*:*:*:*:*:*:*:* Versions 4.16 – 5.37 Vulnerable ·Zyxel
- cpe:2.3:h:zyxel:usg_20w-vpn:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:h:zyxel:vpn50w:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:o:zyxel:zld:*:*:*:*:*:*:*:* Versions 4.30 – 5.37 Vulnerable ·Zyxel
- cpe:2.3:h:zyxel:vpn100:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:h:zyxel:vpn1000:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:h:zyxel:vpn300:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
- cpe:2.3:h:zyxel:vpn50:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Zyxel
Remediation
No fixed version listed by the sources yet.
Fixed in the same release
Records fixed by the same vendor advisory or release, as the CNA lists them.
- Advisory ·
Zyxel ATP series firmware, USG FLEX 50(W) series firmware and 3 more products — zyxel.com/global/en/support/security-advisories/zyxel-secur…
9 records Highest priority Priority MEDIUM 1 MEDIUM, 8 LOW
Other records, highest priority first
- TI-2023-04062 Integer overflow in Zyxel ATP series firmwarePriority MEDIUM 41
- TI-2023-17585 Cross-site scripting in Zyxel ATP series firmwarePriority LOW 28
- TI-2023-19359 Buffer overflow in Zyxel ATP series firmwarePriority LOW 24
Timeline
- 2026-10-02 Threatist record created from CVE-2023-35136
- 2026-10-03 Alias added: GHSA-7pcw-5pmh-x8wr
References
More Zyxel Zld vulnerabilities
- TI-2024-10813 Path traversal in Zyxel ATP series firmware KEVCVSS 3.1CRITICAL 9.8
- TI-2020-15281 A stack-based buffer overflow in fbwifi_continue.cgi on Zyxel UTM and VPN series of… CVSS 3.1CRITICAL 9.8
- TI-2025-08373 Missing authorization in Zyxel ATP series firmware CVSS 3.1HIGH 8.1
- TI-2023-04062 Integer overflow in Zyxel ATP series firmware CVSS 3.1HIGH 7.5
- TI-2024-28064 NULL pointer dereference in Zyxel ATP series firmware CVSS 3.1HIGH 7.5
- TI-2024-28063 OS command injection in Zyxel ATP series firmware CVSS 3.1HIGH 8.1
Sources
- CVE-2023-35136 · CVE Program
- CVE-2023-35136 · NVD
- FIRST EPSS
- GHSA-7pcw-5pmh-x8wr · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences