Is CVE-2026-23829 in the CISA KEV catalog?

No. CVE-2026-23829 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-23829?

CVE-2026-23829 has a CVSS v3 base score of 5.3 (MEDIUM).

What is the EPSS score for CVE-2026-23829?

CVE-2026-23829 has an EPSS score of 1.44% (70th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-23829?

Upgrade mailpit to 1.28.3 or later.

CVE & CISA-KEV Catalog

CVE-2026-23829

MEDIUM

5.3

CVSS v3

NVD

Description

Mailpit is an email testing tool and API for developers. Prior to version 1.28.3, Mailpit's SMTP server is vulnerable to Header Injection due to an insufficient Regular Expression used to validate `RCPT TO` and `MAIL FROM` addresses. An attacker can inject arbitrary SMTP headers (or corrupt existing ones) by including carriage return characters (`\r`) in the email address. This header injection occurs because the regex intended to filter control characters fails to exclude `\r` and `\n` when used inside a character class. Version 1.28.3 fixes this issue.

CWE-93 CWE-150

How to fix

Remediation Available

mailpitNVD

Affected:< 1.28.3Fixed in:1.28.3CVE-2026-23829derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityLow

AvailabilityNone

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

Exploit Intelligence

1.44%probability of exploitation in 30 days

70thpercentile

Moderate risk: more likely to be exploited than 70% of all known CVEs.

References

Patch1

github.com

Exploit1

github.com

Release Notes1

github.com

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-02-23.