Vulnerability in Postalsys Postal-Mime
CVE-2026-125756
postal-mime before 4.2.1 contains a parser differential vulnerability in its address parser that truncates the domain at folding whitespace or comments preceding a dot. Remote attackers can craft From headers that pass SPF/DKIM/DMARC alignment for their own subdomain while PostalMime.parse() reports a spoofed victim sender address.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/postalsys/postal-mime/security/advisories/GHSA-jh3p-792r-98gm (vendor-advisory)
- github.com/postalsys/postal-mime/commit/646725704463839f233472453b7c8306bd1dde21 (patch)
- github.com/postalsys/postal-mime/releases/tag/v4.2.1 (release-notes)
- github.com/postalsys/postal-mime/blob/939a220bd518f54d98a088c315d7227e6215cae3/… (technical-description)
- www.vulncheck.com/advisories/postal-mime-before-4.2.1-sender-spoofing-via-addre… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-125756?
- CVE-2026-125756 is a medium-severity vulnerability in Postalsys Postal-Mime, classified under CWE-436. CVSS score: 5.9/10. Published 2026-11-10.
- How severe is CVE-2026-125756?
- Medium severity. CVSS v3 base score is 5.9 out of 10.