SEPPmail User Web Interface Arbitrary File Write to RCE

published 2026-03-05 8 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-9794

cvss: 9.8; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.9%; EPSS 0.9% chance of exploitation in 30 days, percentile 61%
public exploits: 0; none known

Arbitrary File Write via Path Traversal upload to Remote Code Execution in SeppMail User Web Interface. The affected feature is the large file transfer (LFT).

This issue affects SeppMail: 15.0.2.1 and before

CISA SSVC

Exploitation: Proof of concept is public
Automatable: yes
Technical impact: total
Assessed: 5 mo ago (2026-05-19)

Exploit prediction

0.95% chance of exploitation in the next 30 days, higher than 61% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

labs.infoguard.ch https://labs.infoguard.ch/posts/seppmail_secure_e-mail_gateway_rce_vulnerabilities_cve-2026-2743_cve-2026-7864_cve-2026-44127_cve-2026-44128/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	4.0	10.0	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:A/AU:Y
CNA	4.0	10.0	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:A/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:Y/R:X/V:X/RE:X/U:X
NVD	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

SeppMail SeppMail

Classification

Weakness

CWE-22 Improper Limitation of a Pathname to a Restricted Directory
CWE-434 Unrestricted Upload of File with Dangerous Type

References

Sources

CVE List CVE-2026-2743
NVD CVE-2026-2743

Fencer Vulns 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.

Summary