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Vulnerabilities CVE-2026-67446

CVE-2026-67446

Medium
Open
TLP:CLEAR

Mailpit: Thumbnail generation decodes unbounded image dimensions before scaling

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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.

Details

CVSS Score
5.3
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Confidence
90%
Published
Aug 20, 2026
Last Modified
Aug 20, 2026
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