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CVE-2026-67446— Mailpit: Thumbnail generation decodes unbounded image dimensions before scaling

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.

axllent mailpit是axllent个人开发者开源的一款邮件测试与调试工具。 axllent mailpit 1.30.4之前版本存在资源管理错误漏洞，该漏洞源于在生成缩略图时未先检查解码尺寸、像素数或内存使用情况即完整解码攻击者提供的图像附件，可能导致大量内存和CPU消耗，降低服务可用性。

CVSS 5.3 · Medium EPSS 0.51% · P41

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 1

VendorProduct Version RangeStatus
axllent mailpit < 1.30.4 affected
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I. Basic Information for CVE-2026-67446

Vulnerability Information
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Vulnerability Title
Mailpit: Thumbnail generation decodes unbounded image dimensions before scaling
Source: CVE Program / CVE List V5
Vulnerability Description
Mailpit is an email testing tool and API for developers. Prior to 1.30.4, Mailpit decodes attacker-supplied image attachments into a full raster before checking decoded dimensions, pixel count, or memory use in the GET /api/v1/message/{id}/part/{partID}/thumb endpoint. The Thumbnail handler in server/apiv1/thumbnails.go obtains attachment bytes through storage.GetAttachmentPart(), accepts image/* content, and calls imaging.Decode() with AutoOrientation before imaging.Fill() scales the image to 180 by 120 pixels. A compact image declaring very large dimensions can therefore consume disproportionately large memory and CPU, and opening the message UI can trigger the same endpoint through server/ui-src/components/message/MessageAttachments.vue. This can degrade availability when an unauthenticated client can store the crafted attachment and reach the web API. 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
Vulnerability Title
axllent mailpit 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
axllent mailpit是axllent个人开发者开源的一款邮件测试与调试工具。 axllent mailpit 1.30.4之前版本存在资源管理错误漏洞，该漏洞源于在生成缩略图时未先检查解码尺寸、像素数或内存使用情况即完整解码攻击者提供的图像附件，可能导致大量内存和CPU消耗，降低服务可用性。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
axllent mailpit < 1.30.4 -

II. Public POCs for CVE-2026-67446

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III. Intelligence Information for CVE-2026-67446

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Patches & Fixes for CVE-2026-67446 (1)

Vendor Advisories for CVE-2026-67446 (1)

Vendor Pages for CVE-2026-67446 (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-2026-67445 5.3 MEDIUM Mailpit: SMTP command parser buffers unbounded command lines before syntax rejection
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-2026-67446

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