# CVE-2023-51765: sendmail: sendmail through 8.17.2 allows SMTP smuggling in certain configurations

CVE-2023-51765 is fixed in 8 products on 1 platform, first by DEBIAN-CVE-2023-51765, released December 24, 2023. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2023-51765
- Priority: Routine
- CVSS: 5.3 (medium)
- EPSS: 0.0108
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Dec 24, 2023

## Description

sendmail through 8.17.2 allows SMTP smuggling in certain configurations. Remote attackers can use a published exploitation technique to inject e-mail messages with a spoofed MAIL FROM address, allowing bypass of an SPF protection mechanism. This occurs because sendmail supports <LF>.<CR><LF> but some other popular e-mail servers do not. This is resolved in 8.18 and later versions with 'o' in srv_features.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | sendmail Debian 12.15 (bookworm) | 8.17.1.9-2+deb12u1 | [DEBIAN-CVE-2023-51765](https://patchblox.com/security/data/fix/linux/debian-cve-2023-51765.md) | Dec 24, 2023 |
| Linux | sendmail Debian 13.5 (trixie) | 8.18.1-1 | [DEBIAN-CVE-2023-51765](https://patchblox.com/security/data/fix/linux/debian-cve-2023-51765.md) | Dec 24, 2023 |
| Linux | sendmail Debian 14 | 8.18.1-1 | [DEBIAN-CVE-2023-51765](https://patchblox.com/security/data/fix/linux/debian-cve-2023-51765.md) | Dec 24, 2023 |
| Linux | sendmail amzn 2023 | 8.18.2-2.amzn2023.0.1 | [ALAS2023-2026-1818](https://patchblox.com/security/data/fix/linux/alas2023-2026-1818.md) | Jun 8, 2026 |
| Linux | sendmail-cf amzn 2023 | 8.18.2-2.amzn2023.0.1 | [ALAS2023-2026-1818](https://patchblox.com/security/data/fix/linux/alas2023-2026-1818.md) | Jun 8, 2026 |
| Linux | sendmail-debuginfo amzn 2023 | 8.18.2-2.amzn2023.0.1 | [ALAS2023-2026-1818](https://patchblox.com/security/data/fix/linux/alas2023-2026-1818.md) | Jun 8, 2026 |
| Linux | sendmail-debugsource amzn 2023 | 8.18.2-2.amzn2023.0.1 | [ALAS2023-2026-1818](https://patchblox.com/security/data/fix/linux/alas2023-2026-1818.md) | Jun 8, 2026 |
| Linux | sendmail-doc amzn 2023 | 8.18.2-2.amzn2023.0.1 | [ALAS2023-2026-1818](https://patchblox.com/security/data/fix/linux/alas2023-2026-1818.md) | Jun 8, 2026 |
| Linux | sendmail-milter amzn 2023 | 8.18.2-2.amzn2023.0.1 | [ALAS2023-2026-1818](https://patchblox.com/security/data/fix/linux/alas2023-2026-1818.md) | Jun 8, 2026 |
| Linux | sendmail-milter-debuginfo amzn 2023 | 8.18.2-2.amzn2023.0.1 | [ALAS2023-2026-1818](https://patchblox.com/security/data/fix/linux/alas2023-2026-1818.md) | Jun 8, 2026 |
| Linux | sendmail-milter-devel amzn 2023 | 8.18.2-2.amzn2023.0.1 | [ALAS2023-2026-1818](https://patchblox.com/security/data/fix/linux/alas2023-2026-1818.md) | Jun 8, 2026 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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