Axllent Mailpit up to 1.30.4 smtpd internal/smtpd/smtpd.go readData allocation of resources

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Axllent Mailpit up to 1.30.4. This vulnerability affects the function readData of the file internal/smtpd/smtpd.go of the component smtpd. Performing a manipulation results in allocation of resources. This vulnerability is identified as CVE-2026-67447. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in Axllent Mailpit up to 1.30.4. It has been classified as problematic. This affects the function readData of the file internal/smtpd/smtpd.go of the component smtpd. The manipulation with an unknown input leads to a allocation of resources vulnerability. CWE is classifying the issue as CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. This is going to have an impact on availability. The summary by CVE is:

Mailpit is an email testing tool and API for developers. From 1.30.0 until 1.30.5, Mailpit's internal/smtpd/smtpd.go readData() function calls bufio.Reader.ReadBytes before applying the len(data)+len(line) size check to the completed SMTP DATA line against Server.MaxSize. An unauthenticated SMTP client can send a single line larger than the configured MaxMessageSize, causing the full line to be allocated before Mailpit returns the 552 5.3.4 rejection. This post-fix gap remains after normal multi-line DATA accumulation was bounded, and concurrent oversized lines can create substantial memory pressure beyond the configured message-size cap. This issue is fixed in version 1.30.5.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-67447 since 07/29/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 1.30.5 eliminates this vulnerability.

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Productinfo

Vendor

• Axllent

Name

• Mailpit

Version

• 1.30.0
• 1.30.1
• 1.30.2
• 1.30.3
• 1.30.4

Website

• Product: https://github.com/axllent/mailpit/

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