# Improper input validation in Zyxel USG/ZyWALL series firmware and others

CVE record · `CVE-2022-26531`

- **Identifiers:** `CVE-2022-26531`
- **State:** Confirmed
- **Severity:** CVSS 6.1 Medium
- **Critical:** No
- **CNA:** Zyxel
- **Weakness (CWE):** [CWE-20](https://cwe.mitre.org/data/definitions/20.html)
- **Tags:** [CWE-20](https://agentprime.io/advisories/tag/cwe-20.md)
- **Technologies:** [Zyxel USG/ZyWALL series firmware](https://agentprime.io/advisories/technology/zyxel-usg-zywall-series-firmware.md) · [Zyxel USG FLEX series firmware](https://agentprime.io/advisories/technology/zyxel-usg-flex-series-firmware.md) · [Zyxel ATP series firmware](https://agentprime.io/advisories/technology/zyxel-atp-series-firmware.md) · [Zyxel VPN series firmware](https://agentprime.io/advisories/technology/zyxel-vpn-series-firmware.md) · [Zyxel NSG series firmware](https://agentprime.io/advisories/technology/zyxel-nsg-series-firmware.md) · [Zyxel NXC2500 firmware](https://agentprime.io/advisories/technology/zyxel-nxc2500-firmware.md) · [Zyxel NAP203 firmware](https://agentprime.io/advisories/technology/zyxel-nap203-firmware.md) · [Zyxel NWA50AX firmware](https://agentprime.io/advisories/technology/zyxel-nwa50ax-firmware.md) · [Zyxel WAC500 firmware](https://agentprime.io/advisories/technology/zyxel-wac500-firmware.md) · [Zyxel WAX510D firmware](https://agentprime.io/advisories/technology/zyxel-wax510d-firmware.md)
- **Published:** 24 May 2022
- **Updated:** 3 Aug 2024
- **Reviewed by a person:** No

Published by the CVE Program (CNA: Zyxel) at 24 May 2022, 00:00 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

## Affected products, as the CNA wrote them

- Vendor: Zyxel. Product: USG/ZyWALL series firmware.
  - affected: `4.09 through 4.71`
- Vendor: Zyxel. Product: USG FLEX series firmware.
  - affected: `4.50 through 5.21`
- Vendor: Zyxel. Product: ATP series firmware.
  - affected: `4.32 through 5.21`
- Vendor: Zyxel. Product: VPN series firmware.
  - affected: `4.30 through 5.21`
- Vendor: Zyxel. Product: NSG series firmware.
  - affected: `1.00 through 1.33 Patch 4`
- Vendor: Zyxel. Product: NXC2500 firmware.
  - affected: `<= 6.10(AAIG.3)`
- Vendor: Zyxel. Product: NAP203 firmware.
  - affected: `<= 6.25(ABFA.7)`
- Vendor: Zyxel. Product: NWA50AX firmware.
  - affected: `<= 6.25(ABYW.5)`
- Vendor: Zyxel. Product: WAC500 firmware.
  - affected: `<= 6.30(ABVS.2)`
- Vendor: Zyxel. Product: WAX510D firmware.
  - affected: `<= 6.30(ABTF.2)`

## Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

## Severity and exploitation

- 6.1 Medium, CVSS 3.1: `CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H`, from CNA (Zyxel)

- **CISA KEV:** Not listed.
- **EPSS:** 0.064, the 93rd percentile, on 9 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the CVE Program, published 24 May 2022. New records show when each source confirmed them.

## Sources

- [CVE List: CVE-2022-26531](https://www.cve.org/CVERecord?id=CVE-2022-26531)
- [NVD: CVE-2022-26531](https://nvd.nist.gov/vuln/detail/CVE-2022-26531)

### References from the CNA

- <https://www.zyxel.com/support/multiple-vulnerabilities-of-firewalls-AP-controllers-and-APs.shtml>
- <http://seclists.org/fulldisclosure/2022/Jun/15> (mailing-list)
- <http://packetstormsecurity.com/files/167464/Zyxel-Buffer-Overflow-Format-String-Command-Injection.html>
- <http://packetstormsecurity.com/files/177036/Zyxel-zysh-Format-String-Proof-Of-Concept.html>

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.

## Check whether this affects you

This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it. Compare the affected versions above with what you run.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), `get_advisory` returns this record and `search_advisories` finds related ones. Setup: <https://agentprime.io/mcp.md>
- As JSON: <https://api.agentprime.io/v1/advisories/CVE-2022-26531>
- Everything that needs attention now: <https://agentprime.io/advisories/critical.md>

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The web page: <https://agentprime.io/advisories/CVE-2022-26531/>. Everything for agents: <https://agentprime.io/llms.txt>.