CVE-2026-67446mediumCWE-400CWE-770

CVE-2026-67446: medium-severity vulnerability in axllent mailpit

Mailpit: Thumbnail generation decodes unbounded image dimensions before scaling

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13Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 5.3epss 0.5%
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Affected products
axllent · mailpit
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