VulnerabilityPublished 4 Mar 2026

CVE-2026-2746: SEPPmail Secure Email Gateway · Improper Verification of Cryptographic Signature

Affects SEPPmail Secure Email GatewaySource CVE Database V5

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Not known to be exploited · CVSS 6.9 Medium : upgrade to 15.0.1 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 4.0 base score

6.9Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 5% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 15.0.1

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: Low
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: Low
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Subsequent System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 4 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade SEPPmail Secure Email Gateway to 15.0.1.

Affected software

Product	Affected	Fixed in
SEPPmailSecure Email Gateway	Affected <15.0.1	Fixed in 15.0.1

AI-suggested

To mitigate CVE-2026-2746, organizations should immediately upgrade SEPPmail Secure Email Gateway to version 15.0.1 or later, where the signature verification communication issue is resolved. In parallel, implement enhanced email security controls such as deploying complementary email authentication standards (SPF, DKIM, DMARC) to reduce reliance solely on PGP signatures. Conduct regular audits of email gateway logs and signature verification results to detect anomalies. Train users to recognize signs of forged or suspicious emails despite signature indicators, emphasizing caution with unexpected or unusual messages. Consider deploying additional email security solutions that perform independent signature validation and alerting. Establish incident response procedures specifically addressing forged email detection and reporting. Maintain up-to-date threat intelligence feeds to monitor emerging exploits targeting this vulnerability. Finally, coordinate with SEPPmail support and security advisories to stay informed about patches and mitigations.

Description

SEPPmail Secure Email Gateway before version 15.0.1 does not properly communicate PGP signature verification results, leaving users unable to detect forged emails.

Impact

The primary impact of CVE-2026-2746 is the erosion of trust in email authenticity within organizations using vulnerable SEPPmail Secure Email Gateway versions. Attackers can exploit this flaw to send forged emails that appear to have valid PGP signatures, bypassing user detection and potentially leading to successful phishing attacks, business email compromise, or distribution of malicious content. This can result in financial losses, data breaches, and reputational damage. Since the vulnerability does not require authentication or user interaction, it can be exploited at scale by remote attackers. Organizations in sectors with high reliance on secure email, such as finance, healthcare, government, and critical infrastructure, face increased risk. The inability to detect forged signatures also complicates incident response and forensic investigations, as malicious emails may be misclassified as legitimate. While no known exploits exist currently, the medium severity rating indicates a significant risk that should be addressed promptly to maintain secure communications.

CWE-347Improper Verification of Cryptographic Signature (opens in a new tab)
Base weaknessOWASP Top 10 A04:2025: Cryptographic Failures (opens in a new tab)
The product does not verify, or incorrectly verifies, the cryptographic signature for data.
OWASP Cheat Sheets
XML Security (opens in a new tab)
REST Security (opens in a new tab)
JSON Web Token for Java (opens in a new tab)
REST Assessment (opens in a new tab)
Cross-Site Request Forgery Prevention (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.2 (opens in a new tab)
V3.5.3 (opens in a new tab)
V13.2.6 (opens in a new tab)
Attack patterns
Padding Oracle Crypto Attack (opens in a new tab)
Signature Spoofing by Improper Validation (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

downloads.seppmail.com/extrelnotes/150/ERN15.0.html (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 11 Mar 2026, 20:10 UTC

WeaknessesCWE-347

Technical details

References

Community reviews

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