CVE-2026-125756 (CVSS 5.9)

Description

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.

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CVSS v3.1 Score

5.9

MEDIUM

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

EPSS — Exploit Prediction

0.0039

Probability of exploitation

0.34%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-436 CWE-436

References

Other References

https://github.com/postalsys/postal-mime/blob/939a220bd518f54d98a088c315d7227e6215cae3/src/address-parser.ts#L265 https://github.com/postalsys/postal-mime/commit/646725704463839f233472453b7c8306bd1dde21 https://github.com/postalsys/postal-mime/releases/tag/v4.2.1 https://github.com/postalsys/postal-mime/security/advisories/GHSA-jh3p-792r-98gm https://www.vulncheck.com/advisories/postal-mime-before-4.2.1-sender-spoofing-via-address-parser-domain-truncation

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 5.9 (MEDIUM).

How severe is CVE-2026-125756? +

CVE-2026-125756 has a CVSS v3.1 score of 5.9 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0039, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-125756? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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