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CVE-2026-67445— Mailpit: SMTP command parser buffers unbounded command lines before syntax rejection

Quick assessment

Affected
axllent mailpit
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Mailpit 是一款面向开发者的电子邮件测试工具及 API。在版本 1.30.4 之前，Mailpit 通过内部组件 中的 方法读取 SMTP 命令，该方法使用 进行读取，而在执行 解析命令动词或强制执行 RFC 5321 定义的 512 字节命令行长度限制之前，即可完成整个命令行的读取。因此，未认证的远程 SMTP 客户端可以发送一个过大的单行命令，在语法拒绝或超时发生前即完成全部内存分配。由于该路径位于 DATA 命令之前，正常的 和 DATA 限制不适用于此阶段。此外，相同的命令读取器也被 、 和 的续行处

CVSS 5.3 · Medium EPSS 0.37% · P30

Affected Version Matrix 1

VendorProduct Version RangeStatus
axllent mailpit < 1.30.4 affected
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I. Basic Information for CVE-2026-67445

Vulnerability Information
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Vulnerability Title
Mailpit: SMTP command parser buffers unbounded command lines before syntax rejection
Source: CVE Program / CVE List V5
Vulnerability Description
Mailpit is an email testing tool and API for developers. Prior to 1.30.4, Mailpit reads SMTP commands through internal/smtpd/smtpd.go session.readLine() using bufio.Reader.ReadString before session.parseLine() parses the verb or the RFC 5321 512-octet command-line limit is enforced. An unauthenticated remote SMTP client can send an oversized single command line that is fully allocated before syntax rejection or timeout, and the normal MaxMessageSize and DATA limits do not apply to this pre-DATA path. The same command reader is used by handleAuthLogin(), handleAuthPlain(), and handleAuthCramMD5() continuation lines, so concurrent oversized inputs can create memory pressure and reduce service availability. This issue is fixed in version 1.30.4.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
axllent mailpit < 1.30.4 -

II. Public POCs for CVE-2026-67445

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III. Intelligence Information for CVE-2026-67445

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Patches & Fixes for CVE-2026-67445 (1)

Vendor Advisories for CVE-2026-67445 (1)

Vendor Pages for CVE-2026-67445 (1)

Same Patch Batch · axllent · 2026-08-20 · 4 CVEs total

CVE-2026-67448 6.5 MEDIUM Mailpit: WebSocket origin check bypass via percent-encoded path (regression of CVE-2026-22
CVE-2026-67446 5.3 MEDIUM Mailpit: Thumbnail generation decodes unbounded image dimensions before scaling
CVE-2026-67447 5.3 MEDIUM Mailpit: SMTP DATA line reader buffers over-limit input before size enforcement

IV. Related Vulnerabilities

Same product: mailpit
Same vendor: axllent
Same weakness: CWE-400

V. Comments for CVE-2026-67445

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