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CVE-2026-67446 medium CVSS 5.3

Vulnerability in github.com/axllent/mailpit (CVE-2026-67446)

Summary

Vulnerability in github.com/axllent/mailpit (CVE-2026-67446). Risk of unauthorized operations or information disclosure. Exploitable via GET /api/v1/message/{id}/part/{partID}/thumb. Mitigation: upgrade to 1.30.4 or later.

Original description

The description as published by the source.

Summary

Mailpit's thumbnail endpoint decodes attacker-supplied image attachments into a full raster before checking any decoded-pixel, dimension, or memory budget. A remote client that can store an email and reach the default web API can supply a compact high-dimension image, then request /api/v1/message/{id}/part/{partID}/thumb to force server-side memory and CPU work far larger than the encoded attachment size before Mailpit returns a 180x120 thumbnail.

Technical Details

The route is registered as GET /api/v1/message/{id}/part/{partID}/thumb in server/server.go. The handler in server/apiv1/thumbnails.go loads the requested attachment and accepts any part whose content type begins with image/:

a, err := storage.GetAttachmentPart(id, partID)
// ...
if !strings.HasPrefix(a.ContentType, "image/") {
    blankImage(a, w)
    return
}

buf := bytes.NewBuffer(a.Content)
img, err := imaging.Decode(buf, imaging.AutoOrientation(true))

storage.GetAttachmentPart() reparses the stored raw email and returns the matching attacker-supplied attachment bytes. Thumbnail() then calls imaging.Decode() before any check on declared dimensions or estimated decoded bytes. The subsequent imaging.Fill(img, 180, 120, ...), imaging.Clone(), and JPEG encode only happen after the full image has already been decoded.

The thumbnail output is fixed at 180x120, so the endpoint does not need to decode arbitrarily large rasters. The current implementation lets a small c…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-67446 has been found in github.com/axllent/mailpit.
Attackers can target a specific entry point like GET /api/v1/message/{id}/part/{partID}/thumb over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.3/10.
What to do: upgrade github.com/axllent/mailpit to 1.30.4 or later.
If unsure, ask your IT team or search "github.com/axllent/mailpit CVE-2026-67446" on the vendor's site.

CVE-2026-67446 (github.com/axllent/mailpit) — CWE-400 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: GET /api/v1/message/{id}/part/{partID}/thumb / PartID / develop / cd7661fd5b23cce1e218b583b21e157cfa612051
Patched: 1.30.4 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-400) exists in github.com/axllent/mailpit. Attackers reach the vulnerable code path via GET /api/v1/message/{id}/part/{partID}/thumb without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of github.com/axllent/mailpit. Attack surface: GET /api/v1/message/{id}/part/{partID}/thumb / PartID / develop / cd7661fd5b23cce1e218b583b21e157cfa612051.

🔥 Severity

Severity: Medium (CVSS 5.3/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 1.30.4.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual GET /api/v1/message/{id}/part/{partID}/thumb requests with malformed payloads or SQL meta-characters. Run grep -r 'github.com/axllent/mailpit' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'github.com/axllent/mailpit' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で github.com/axllent/mailpit を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Hunt for indicators of compromise detect 
    grep 'GET /api/v1/message/{id}/part/{partID}/thumb' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで GET /api/v1/message/{id}/part/{partID}/thumb への異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。

  3. 3
    Apply patch patch 
    Upgrade github.com/axllent/mailpit to 1.30.4

    ステージング環境で 1.30.4 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスと、Step 2 で見つけた異常検知の続報チェックを含めること。

  4. 4
    Post-deployment verification verify 
    Replay attack against GET /api/v1/message/{id}/part/{partID}/thumb on staging to confirm patch closes the vector

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 2 と同じログクエリでアラート再発が無いか継続監視。

Affected packages

go github.com/axllent/mailpit
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.30.4"}]}]

References

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