CVE-2026-125756 json
postal-mime before 4.2.1 Sender Spoofing via Address Parser Domain Truncation
published 2d ago modified yesterday also EUVD-2026-121239 , GHSA-jh3p-792r-98gm
Unreviewed: the maintainers' own advisory
Published by the maintainers on their GitHub repository postalsys/postal-mime. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.
- cvss
- 5.9
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 33%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- npm postal-mime 4.2.1
- postalsys postal-mime 4.2.1
Is CVE-2026-125756 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- yesterday
Exploit prediction
0.39% chance of exploitation in the next 30 days, higher than 33% of all scored CVEs (FIRST EPSS, 2026-11-11).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 8.2 | CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N |
| CNA | 3.1 | 5.9 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N |
| CNA | 4.0 | 8.2 | CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| npm | postal-mime | <=4.2.0 |
4.2.1 |
Affected products
- postalsys postal-mime
Classification
- Weakness
-
- CWE-436 Interpretation Conflict
References
-
github.com
/postalsys/postal-mime/commit/646725704463839f233472453b7c8306bd1dde21
patch
-
github.com
/postalsys/postal-mime/security/advisories/GHSA-jh3p-792r-98gm
vendor-advisory, advisory
-
github.com
/postalsys/postal-mime/releases/tag/v4.2.1
release-notes
-
github.com
/postalsys/postal-mime/blob/939a220bd518f54d98a088c315d7227e6215cae3/src/address-parser.ts#L265
technical-description
-
vulncheck.com
/advisories/postal-mime-before-4.2.1-sender-spoofing-via-address-parser-domain-truncation
third-party-advisory
Sources
- CVE List CVE-2026-125756
- NVD CVE-2026-125756
- Maintainer advisory GHSA-jh3p-792r-98gm
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
The maintainers of postalsys/postal-mime published their own advisory on GitHub. Reviewed sources take precedence over it.