CVE-2024-27938: Postal is an open source SMTP server. Postal versions less than 3.0.0 are vulnerable to SMTP Smuggling attacks which may allow incoming e-mails to be ...

Description

Postal is an open source SMTP server. Postal versions less than 3.0.0 are vulnerable to SMTP Smuggling attacks which may allow incoming e-mails to be spoofed. This, in conjunction with a cooperative outgoing SMTP service, would allow for an incoming e-mail to be received by Postal addressed from a server that a user has 'authorised' to send mail on their behalf but were not the genuine author of the e-mail. Postal is not affected for sending outgoing e-mails as email is re-encoded with `<CR><LF>` line endings when transmitted over SMTP. This issue has been addressed and users should upgrade to Postal v3.0.0 or higher. Once upgraded, Postal will only accept End of DATA sequences which are explicitly `<CR><LF>.<CR><LF>`. If a non-compliant sequence is detected it will be logged to the SMTP server log. There are no workarounds for this issue.

Metrics

CVSS 3.1

5.3/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS Probability

0.66%

47.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Postalserver	Postal	< 3.0.0

References

https://github.com/postalserver/postal/commit/0140dc4Patch
https://github.com/postalserver/postal/security/advisories/GHSA-j42r-6c99-hqf2Vendor Advisory
https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwideTechnical Description
https://www.postfix.org/smtp-smuggling.htmlExploit
https://github.com/postalserver/postal/commit/0140dc4Patch
https://github.com/postalserver/postal/security/advisories/GHSA-j42r-6c99-hqf2Vendor Advisory
https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwideTechnical Description
https://www.postfix.org/smtp-smuggling.htmlExploit

Timeline

Published: Mar 11, 2024
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2024-27938?

Postal is an open source SMTP server. Postal versions less than 3.0.0 are vulnerable to SMTP Smuggling attacks which may allow incoming e-mails to be spoofed. This, in conjunction with a cooperative outgoing SMTP service, would allow for an incoming e-mail to be received by Postal addressed from a server that a user has 'authorised' to send mail on their behalf but were not the genuine author of the e-mail. Postal is not affected for sending outgoing e-mails as email is re-encoded with `<CR><LF>` line endings when transmitted over SMTP. This issue has been addressed and users should upgrade to Postal v3.0.0 or higher. Once upgraded, Postal will only accept End of DATA sequences which are explicitly `<CR><LF>.<CR><LF>`. If a non-compliant sequence is detected it will be logged to the SMTP server log. There are no workarounds for this issue.

How severe is CVE-2024-27938?

CVE-2024-27938 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 0.66% probability of exploitation in the next 30 days.

How do I fix CVE-2024-27938?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.