What is CVE-2024-27938?

CVE-2024-27938 is a medium-severity vulnerability in Postalserver Postal, classified under Improper Encoding or Escaping of Output. CVSS score: 5.3/10. Published 2024-03-11.

How severe is CVE-2024-27938?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Is CVE-2024-27938 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Postalserver Postal

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.

Published 2024-03-11 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.007 (49.9th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 50th percentile — 49.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000

Affected products

Postalserver Postal — versions < 3.0.0

Weakness classification (CWE)

CWE-116 — Improper Encoding or Escaping of Output

Public proof-of-concept exploits

fkie-cad/nvd-json-data-feeds

References

github.com/postalserver/postal/security/advisories/GHSA-j42r-6c99-hqf2 (Vendor Advisory)
github.com/postalserver/postal/commit/0140dc4 (Patch)
sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide (Technical Description)
www.postfix.org/smtp-smuggling.html (Exploit)

Frequently asked questions

What is CVE-2024-27938?: CVE-2024-27938 is a medium-severity vulnerability in Postalserver Postal, classified under Improper Encoding or Escaping of Output. CVSS score: 5.3/10. Published 2024-03-11.
How severe is CVE-2024-27938?: Medium severity. CVSS v3 base score is 5.3 out of 10.
Is CVE-2024-27938 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.