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

> An attacker can cause denial of service by uploading crafted image attachments that consume excessive memory and CPU during thumbnail generation.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 Aug 2026
- **Updated:** 21 Aug 2026
- **Also known as:** GHSA-75mr-qw9x-3r39, GO-2026-6359

## What is CVE-2026-67446?

CVE-2026-67446 is a medium-severity denial of service vulnerability in axllent mailpit, published on 20 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-67446?

3 open source packages ship an affected version, including github.com/axllent/mailpit.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/axllent/mailpit` | Go | All versions | 1.30.4 |
| `github.com/axllent/mailpit` | Go | All versions | 1.30.4 |
| `github.com/axllent/mailpit` | Go | All versions | 1.30.4 |

## How do I fix CVE-2026-67446?

Upgrade github.com/axllent/mailpit to 1.30.4 or later.

## Is CVE-2026-67446 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-67446 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-67446 and fix it if it is affected.

What it is: CVE-2026-67446 is a medium-severity denial of service vulnerability in axllent mailpit, published on 20 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-67446 exists.

Affected packages and fixed versions:
- github.com/axllent/mailpit (Go): affected all versions; fixed in 1.30.4
- github.com/axllent/mailpit (Go): affected all versions; fixed in 1.30.4
- github.com/axllent/mailpit (Go): affected all versions; fixed in 1.30.4

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-67446/ (Markdown: https://insights.sbomify.com/CVE-2026-67446/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-67446
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-67446
- OSV: https://osv.dev/vulnerability/CVE-2026-67446

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-67446/
Summaries are generated and may contain mistakes; the official description above is the record.