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CVE-2026-91971 medium CVSS 6.5

Vulnerability in code.vikunja.io/api (CVE-2026-91971)

Summary

Vulnerability in code.vikunja.io/api (CVE-2026-91971). Risk of unauthorized operations or information disclosure. Exploitable via PUT /api/v1/user/settings/avatar/upload. Mitigation: upgrade to 2.6.0 or later.

Original description

The description as published by the source.

Summary

The 50-megapixel decode guard exists only on the task-attachment preview path. Avatar and project-background uploads decode uploaded images with no pixel cap. Worse, the avatar resize fixes the output height at 1024 and derives the width from the aspect ratio, so a tiny extreme-aspect-ratio PNG expands to an enormous output image — an input-side pixel cap would not catch it.

Details

The only maxPixels check (50MP) is in TaskAttachment.GetPreview (pkg/models/task_attachment.go ~lines 332-338). No such check guards:

  • avatar upload: pkg/modules/avatar/upload/upload.go (~lines 82, 137, 141)
  • project background: pkg/modules/background/handler/background.go (~lines 174, 269, 289)

imaging.Resize(img, 0, 1024, imaging.Lanczos) (upload.go ~line 141) fixes height=1024 and derives width from the aspect ratio: a 20000x10 input yields a ~2,048,000 x 1024 output (~2.1 billion pixels), so a few-hundred-byte file drives huge CPU and memory.

PoC (verified at runtime against v2.5.0)

PUT /api/v1/user/settings/avatar/upload   avatar=8000x8000 PNG (64MP, 192KB) -> 200 (accepted; exceeds the 50MP attachment cap)
PUT /api/v1/user/settings/avatar/upload   avatar=20000x10 PNG (681 bytes)    -> 200 after ~19.6s of server processing

Contrast (guard present): uploading the 64MP PNG as a task attachment and requesting its preview returns in ~1ms without decoding — GetPreview rejects it via maxPixels and falls back to the raw file.

Impact

A small craft…

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-2026-91971 has been found in code.vikunja.io/api.
Attackers can target a specific entry point like PUT /api/v1/user/settings/avatar/upload over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 6.5/10.
What to do: upgrade code.vikunja.io/api to 2.6.0 or later.
If unsure, ask your IT team or search "code.vikunja.io/api CVE-2026-91971" on the vendor's site.

CVE-2026-91971 (code.vikunja.io/api) — CWE-400 / CVSS v3 6.5
Attack vector: remote (network-reachable) / no user interaction
Attack surface: PUT /api/v1/user/settings/avatar/upload / maxPixels / TaskAttachment.GetPreview / GetPreview
Patched: 2.6.0 — 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 code.vikunja.io/api. Attackers reach the vulnerable code path via PUT /api/v1/user/settings/avatar/upload.

📍 Affected scope

Check the vendor advisory for the affected versions of code.vikunja.io/api. Attack surface: PUT /api/v1/user/settings/avatar/upload / maxPixels / TaskAttachment.GetPreview / GetPreview.

🔥 Severity

Severity: Medium (CVSS 6.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 2.6.0.

🛡️ 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 PUT /api/v1/user/settings/avatar/upload requests with malformed payloads or SQL meta-characters. Run grep -r 'code.vikunja.io/api' . 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 'code.vikunja.io/api' . | 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 code.vikunja.io/api 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 'PUT /api/v1/user/settings/avatar/upload' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで PUT /api/v1/user/settings/avatar/upload 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 code.vikunja.io/api to 2.6.0

    ステージング環境で 2.6.0 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 PUT /api/v1/user/settings/avatar/upload 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 code.vikunja.io/api
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.6.0"}]}]

References

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