exim4: Exim before 4.97.1 allows SMTP smuggling in certain PIPELINING/CHUNKING configurations
CVE-2023-51766 is fixed in 6 products on 1 platform, first by exim4 4.90.1-1ubuntu1.10+esm3, released December 23, 2023. It is not reported as exploited. Patch Radar priority: Routine.
Exim before 4.97.1 allows SMTP smuggling in certain PIPELINING/CHUNKING 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 Exim supports <LF>.<CR><LF> but some other popular e-mail servers do not.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| exim4 · Debian 11.6 (bullseye) | 4.94.2-7+deb11u2 | DSA-5597-1 | Jan 4, 2024 |
| exim4 · Debian 12.15 (bookworm) | 4.96-15+deb12u4 | DSA-5597-1 | Jan 4, 2024 |
| exim4 · Debian 13.5 (trixie) | 4.97-3 | DEBIAN-CVE-2023-51766 | Dec 24, 2023 |
| exim4 · Debian 14 | 4.97-3 | DEBIAN-CVE-2023-51766 | Dec 24, 2023 |
| exim4 · Ubuntu 18.04.6 LTS (bionic) | 4.90.1-1ubuntu1.10+esm3 | exim4 4.90.1-1ubuntu1.10+esm3 | Dec 23, 2023 |
| exim4 · Ubuntu 20.04 LTS (focal) | 4.93-13ubuntu1.10 | exim4 4.93-13ubuntu1.10 | Dec 23, 2023 |
| exim4 · Ubuntu 22.04.1 LTS (jammy) | 4.95-4ubuntu2.5 | exim4 4.95-4ubuntu2.5 | Dec 23, 2023 |
| exim4 · Ubuntu 24.10 (oracular) | 4.97-3 | exim4 4.97-3 | Jan 16, 2026 |
| exim4 · Ubuntu 25.04 (plucky) | 4.97-3 | exim4 4.97-3 | Jan 16, 2026 |
| exim4-base · Ubuntu 18.04.6 LTS (bionic) | 4.90.1-1ubuntu1.10+esm3 | exim4-base 4.90.1-1ubuntu1.10+esm3 | Dec 23, 2023 |
| exim4-base · Ubuntu 20.04 LTS (focal) | 4.93-13ubuntu1.10 | exim4-base 4.93-13ubuntu1.10 | Dec 23, 2023 |
| exim4-base · Ubuntu 22.04.1 LTS (jammy) | 4.95-4ubuntu2.5 | exim4-base 4.95-4ubuntu2.5 | Dec 23, 2023 |
| exim4-base · Ubuntu 24.10 (oracular) | 4.97-3 | exim4-base 4.97-3 | Jan 16, 2026 |
| exim4-base · Ubuntu 25.04 (plucky) | 4.97-3 | exim4-base 4.97-3 | Jan 16, 2026 |
| exim4-config · Ubuntu 18.04.6 LTS (bionic) | 4.90.1-1ubuntu1.10+esm3 | exim4-config 4.90.1-1ubuntu1.10+esm3 | Dec 23, 2023 |
| exim4-config · Ubuntu 20.04 LTS (focal) | 4.93-13ubuntu1.10 | exim4-config 4.93-13ubuntu1.10 | Dec 23, 2023 |
| exim4-config · Ubuntu 22.04.1 LTS (jammy) | 4.95-4ubuntu2.5 | exim4-config 4.95-4ubuntu2.5 | Dec 23, 2023 |
| exim4-config · Ubuntu 24.10 (oracular) | 4.97-3 | exim4-config 4.97-3 | Jan 16, 2026 |
| exim4-config · Ubuntu 25.04 (plucky) | 4.97-3 | exim4-config 4.97-3 | Jan 16, 2026 |
| exim4-daemon-heavy · Ubuntu 18.04.6 LTS (bionic) | 4.90.1-1ubuntu1.10+esm3 | exim4-daemon-heavy 4.90.1-1ubuntu1.10+esm3 | Dec 23, 2023 |
| exim4-daemon-heavy · Ubuntu 20.04 LTS (focal) | 4.93-13ubuntu1.10 | exim4-daemon-heavy 4.93-13ubuntu1.10 | Dec 23, 2023 |
| exim4-daemon-heavy · Ubuntu 22.04.1 LTS (jammy) | 4.95-4ubuntu2.5 | exim4-daemon-heavy 4.95-4ubuntu2.5 | Dec 23, 2023 |
| exim4-daemon-heavy · Ubuntu 24.10 (oracular) | 4.97-3 | exim4-daemon-heavy 4.97-3 | Jan 16, 2026 |
| exim4-daemon-heavy · Ubuntu 25.04 (plucky) | 4.97-3 | exim4-daemon-heavy 4.97-3 | Jan 16, 2026 |
| exim4-daemon-light · Ubuntu 18.04.6 LTS (bionic) | 4.90.1-1ubuntu1.10+esm3 | exim4-daemon-light 4.90.1-1ubuntu1.10+esm3 | Dec 23, 2023 |
| exim4-daemon-light · Ubuntu 20.04 LTS (focal) | 4.93-13ubuntu1.10 | exim4-daemon-light 4.93-13ubuntu1.10 | Dec 23, 2023 |
| exim4-daemon-light · Ubuntu 22.04.1 LTS (jammy) | 4.95-4ubuntu2.5 | exim4-daemon-light 4.95-4ubuntu2.5 | Dec 23, 2023 |
| exim4-daemon-light · Ubuntu 24.10 (oracular) | 4.97-3 | exim4-daemon-light 4.97-3 | Jan 16, 2026 |
| exim4-daemon-light · Ubuntu 25.04 (plucky) | 4.97-3 | exim4-daemon-light 4.97-3 | Jan 16, 2026 |
| eximon4 · Ubuntu 18.04.6 LTS (bionic) | 4.90.1-1ubuntu1.10+esm3 | eximon4 4.90.1-1ubuntu1.10+esm3 | Dec 23, 2023 |
| eximon4 · Ubuntu 20.04 LTS (focal) | 4.93-13ubuntu1.10 | eximon4 4.93-13ubuntu1.10 | Dec 23, 2023 |
| eximon4 · Ubuntu 22.04.1 LTS (jammy) | 4.95-4ubuntu2.5 | eximon4 4.95-4ubuntu2.5 | Dec 23, 2023 |
| eximon4 · Ubuntu 24.10 (oracular) | 4.97-3 | eximon4 4.97-3 | Jan 16, 2026 |
| eximon4 · Ubuntu 25.04 (plucky) | 4.97-3 | eximon4 4.97-3 | Jan 16, 2026 |
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